Disks break. It's a fact of life. If a disk is in daily use (as most student disks are) it will wear out in twelve months or less. (Much, much less if it's carried in a pocket or soaked in Coke.) Disks that sit in safe-deposit boxes, on the other hand, will last from ten to fifteen years, but they too will break eventually. As those of us who've suffered disk loss know from experience, the only way to guarantee that your data is safe is to have lots of copies. In other words, "Backup, backup, backup!!!!!"
Humans being what they are, however, they didn't back up enough.
Now
they're coming to you with diskette in hand begging to recover their
thesis, their accounting records, or the PowerPoint presentation
they're supposed to give in ten minutes. This document is (I
hope) a step-by-step approach to doing that. It's written
assuming the audience is a computer consultant who'll be doing this for
a client, but it certainly could be used by anyone who has the right
tools and enough courage to attack the diskette. I assume that
you have a couple of long shots: an old copy of the DOS version
of Norton Utilities available on a machine that will run it, and
up-to-date copies of Norton Utilities for Windows and Macintosh on
appropriate machines. Along with that root access to a Linux
machine will also be useful; there are some nice tools for Linux that
can retrieve unknown stuff off of DOS/Windows/Macintosh diskettes even
when the directory stuff is toast.
Good luck.
Disks come in two types: DOS/Windows and Macintosh. Ask what kind of computer they're using. If they say "Windows", then it's almost certainly a Windows disk, as very few Windows machines are equipped to read Mac diskettes. If they say "Macintosh", then it could be either one. Macs have been equipped with software to read Windows disks for a long time now, and when you purchase a disk it's almost always formatted for Windows, so many Mac users don't even know they're using Windows disks.
Open the write-protect shutter and insert it in a Macintosh. If it's in good enough shape to mount, the icon will appear on the Desktop. If it's a PC disk, the letters "PC" will appear on the disk icon. Jump to "Repairing a DOS/Windows Diskette". If not, it's probably a Mac disk; go to "Repairing a Macintosh Diskette".
If it won't mount, put it in a DOS/Win3x/Win9x machine and run Norton Diskedit by typing
diskedit a: /m
at a command prompt or at the "Start --> Run" window. (You may have to add the full pathname to the diskedit command to get it to run, and diskedit will need to have its properties set to run in MS-DOS mode under Windows 9x.) The "/m" tells Diskedit to start up in maintenance mode. You'll be asked if the disk is 720K or 1.44MB; respond 1.44 MB.
Diskedit will display the first sector of the diskette (disks are divided into sectors) in hexadecimal. [If the diskette is a double-density Mac diskette -- scarce as hen's teeth nowadays -- you won't be able to read it at all, so that's a good sign that you should proceed to "Repairing a Macintosh Diskette".] Typically, a Macintosh diskette will have the first sector of the disk filled with "F6", with the name of the disk somewhere around sector 3 (press {Page Down}to see more). A Windows disk should have the boot sector there, with the version of DOS or Windows the disk was formatted under listed followed by lots of incomprehensible garbage. You may see the words "Non-system disk or disk error". This is normal, as there is a small program on the disk that displays that message if you start the machine with a non-bootable disk in the floppy drive.
Of course, this assumes that sector 1 is readable; if you get a disk error, then all bets are off. Try paging down to see if any other sectors will read. On a DOS/Windows disk the directory will start around sector 19; pressing {F4}should display the file names, sizes and creation dates. A Macintosh disk should have the directory starting somewhere around sector 27 or 28 (it varies).
Why bother with all this? Because using the wrong version of Disk Doctor on a disk will not fix it; it will destroy it. So you have to make sure that "Macintosh" disk isn't really a Windows disk before you start desperate measures to recover it.
As long as you're in Diskedit, you might as well have a look around before using some other tool. Page through sectors 0 through 32 and see if those sectors work. They're very important; they store the File Allocation Table (which tells which clusters belong to which chain) and the directory (which tells which files are on disk, how large they are, and where they start). The layout is as follows:
Boot area: sector 0First FAT: sectors 1 -- 9
Second FAT: sectors 10 -- 18
Root directory: sectors 19 -- 32
If you get data errors in this area it's going to be tough to fix the diskette; jump to "Reviving a Diskette" and/or "Desperate Measures -- Directory Errors and Physical Damage".
If you don't get data errors in this area, move back to sector 1 and press {F5}, the FAT editor view. The File Allocation Table lists "cluster chains" indicating a sequence of disk clusters making up a file. (In the case of a diskette a cluster is equal to one sector, but on other disks it may be more than one sector.) You should see a series of mostly-consecutive numbers beginning with three and increasing. There's a number for every cluster that indicates the next cluster in the file. Zeros indicate that the cluster is not in use. Every so often an "<EOF>" marker should appear; that marks (big surprise) the end of a file. There will probably be numbers that jump outside the normal sequence (i.e., 3, 4, 5, 27, 7, 8, 9, 10). Those out-of-sequence numbers are locations where DOS/Windows couldn't write a file in contiguous clusters because it ran into another file, so it skipped to the numbered cluster. For example, in the sequence above one file started at cluster 2, used clusters 3 through 5, and then jumped to cluster 27. This is disk fragmentation, and it is a problem when recovering files when the File Allocation Table is damaged because you're not completely sure what clusters belong to what file.
If the pattern of numbers doesn't seem to make any sense, press {F3} to view the sector in ASCII mode. If you see recognizable text, then some program has gone insane and written the wrong information in the FAT. This is not necessarily a disaster, as there are two copies of the FAT on any diskette. Page down to sector 10, press {F5} to switch to FAT mode, and see if you see the same thing as sector 1. If not, you're in luck; the second copy may be all right. If you do, the insane program has been thorough in writing the wrong info into the FAT and overwrote both copies. The difficulty of recovery has just gone up by at least one order of magnitude, because you're going to have to guess which clusters go into which file. Jump to "Recovering Files from a DOS/Windows Diskette".
Now go down to sector 19 and press {F4}, the directory view. If you're lucky, you'll see a list of filenames, each on a line with the pertinent information about size, first cluster and creation date. There may be lines containing "bad directory information"; this could be Windows32 long filenames (if you're using an older version of DiskEdit -- version 4 and later will mark it as "LFN", for "Long File Name"). Don't worry too much about them as long as you see a real filename once in a while. If you can read the FAT and the directory, then the disk is an excellent candidate for repair. If you have a good FAT but a broken directory, you may still be OK. The files will be recoverable, but you won't know their names.
Exit DiskEdit and start Norton Disk Doctor. Select "Diagnose Disk", then the floppy drive, then "Begin Test". Answer the questions. Disk Doctor will do its best to repair the bad information in the FAT and directory areas. Then it will check the entire disk for bad sectors, attempt to move the data from the bad sectors into good ones, and mark the bad ones as bad in the FAT so DOS/Windows doesn't try to use them again. When it's finished, you should have a disk on which at least some of the files will be readable. If there are cluster chains in the FAT that don't go with a named file in the directory, Disk Doctor will create new files named "FILEnnnn._DD". Your client will get the fun task of opening all the "*._DD" files to find out what they were.
If the File Allocation Table is mangled, but the directory still shows filenames, you may be able to recover at least the text in the file. Start Diskedit and examine the directory area (press {Alt/O}r and select "A:\"). One of the pieces of information is the starting cluster. Make a list of the filenames, their sizes, and the starting cluster number for each file. Then take the size of the file and divide it by 512, and you'll get a number that is approximately the number of clusters in the file. Add that to the starting number and you'll have the ending cluster, assuming that the disk isn't fragmented. For each file in the list, do the following:
After you've done this for all the files on disk, leave DiskEdit and try opening those files. In some (lucky) cases, the file will open. In more cases, the program -- or the machine -- will crash. Restart and try the next file. For those that don't work, assuming they're word processing documents of some kind or another, try the instructions in "Recovering Text from Word Documents". For Excel documents, try the suggestions in Microsoft's KnowledgeBase articles on the subject at http://sup port.microsoft.com/support/kb/articles/Q109/6/75.ASP or http://sup port.microsoft.com/support/kb/articles/Q142/1/17.asp.
If files are fragmented, you may be able to find the pieces of the file by scanning through the clusters. This works fairly well with ordinary text files, but who uses ordinary text files anymore? (Well...HTML files are ordinary text files, and you might be able to track the codes through.) Scan through the disk, keeping track of the clusters that belong to the file. Then select groups of contiguous clusters with {Alt/O}L and write each piece to a separate file on the hard disk. When you're finished you can glue all the file pieces together with this DOS command at the command prompt:
COPY /B PIECE1+PIECE2+PIECE3+PIECE4 RECOVER.TXT
If the FAT and the directory are both toast, you may still be able to recover some of the words on that diskette. If all you have is Norton Utilities on a DOS box, try this. Start DiskEdit, point it at drive A: and do the following:
Repairing a Mac diskette is mostly autopilot.
When you're finished you'll either have a diskette that works, or Disk Doctor will throw up its hands and recommend that you use Volume Recover to recover the files from the disk. That works great...if the machine the disk was in last had Norton Filesaver installed on it. Without the FileSaver information, Volume Recover is useless. Go on to "Recovering Files from a Macintosh Diskette".
Recovering files from a Mac diskette is a little trickier. You can recover both erased files and "real", or unerased files, so this is also the technique that you'd use to recover a file that someone deleted before they emptied the Trash.
Hopefully the files in the Recovered Files folder will be openable by their creating applications. If not, try the technique in the section "Recovering Text from Word Documents". If Unerase doesn't find any files, you may still be able to recover some text from the disk by copying off the clusters to a file on a Windows machine. Bear in mind that this won't work on a double-density diskette, and jump to the last section of "Recovering Files from a DOS/Windows Diskette".
Word 97, 98 and 2000 provide an excellent tool for recovering Word documents that are corrupted but are on perfectly good diskettes.
Word will open the file and extract all the printable text. You'll want to clean up the extra information at the beginning and end of the document. Formatting and embedded objects will be lost. (Another good reason to keep your documents simple!)
Another trick that occasionally works; if you have an old Macintosh with Word 6 and the Word 97/98 translators installed, try opening the Word document with it. Sometimes -- and it's only sometimes -- the Word 97/98 translator will discard the damaged parts of the file and open the rest. It's worth a try.
A disk that complains about "bad sectors" may be a physical problem (a scratch or hole in the oxide coating on the disk) or it may simply be misformatted by a program that got confused or a drive that malfunctioned. If the latter is the case, it can often be saved by reviving it.
This technique will work on either Windows or Macintosh high-density diskettes or double-density PC diskettes.
DiskTool will copy as much information as possible off of each track of the diskette, reformat the track, and write the information back. Now go back and run Disk Doctor (on a machine appropriate to the diskette type). With luck that will fix many of the problems.
Sometimes none of the tricks above will work. Sometimes you get read errors displaying the directory of a Windows disk. Disk Doctor will report "2000 clusters in 689 chains", which is highly unlikely -- that says there are 689 lost files on the disk, which is more than you can put in the root directory (that's a max of 512). DiskEdit will give read errors in the directory or file allocation table, and DiskTool doesn't help because of physical damage to the diskette -- you can't write a good copy back because the oxide coating is scratched or eroded to the point where it simply won't store information any more.
If that's the case, try this: use DOS DISKCOPY to make a copy of the diskette. Ignore the warnings about read error on various tracks and the "this disk may be unusable" message at the end. Now work on the copy of the diskette, not the original.
Use DiskTool to look at the first and second FATs. Do either of them make sense? If they look alike and usable, skip the next step. If only one does, take the one that does make sense and write it to the other one. Choose the good one from the Object menu, then select "Write object to..." from the Tools menu. When it asks where to write it, choose "to Sectors", then the appropriate disk, then the first sector of the FAT you're copying to. (The location of the two file allocation tables will be displayed, so you don't have to remember it.)
Now look at the directory. Does it make sense, or are there sectors with unusable garbage on them? If there are, press <F2> to switch to hex mode and write zeroes in that sector. If you have a usable FAT, you can at least get files with unknown names out of the disk. You can figure out what they were later. Once you've zeroed out all of the unusable sectors, exit DiskEdit and run Disk Doctor again. It should find some lost clusters in some chains; let Disk Doctor convert them to files. Once that's finished, examine the files with extension "_DD" with LIST or a similar file-display tool and figure out what they are (see the Zip Disks section for more tips on doing this). Rename them accordingly.
If a usable FAT didn't get copied to the new disk, use DiskEdit to examine the old disk; one of the FATs on the old disk may still be usable. If you find one that looks good, use "Write object to..." to copy the FAT to a file on your hard disk. Then change drives to your hard disk, and use "Object -> File" to examine the file you just created. Now put the new disk into the drive and use "Write Object to..." to write the copied FAT to both of the File Allocation Tables on the copied disk. With a little luck, you now have something for Disk Doctor to work with.
The nicest thing about working on a copy of the original disk, of
course, is that if you really screw it up you can copy the disk again
and start over.
Sometimes you'll encounter a diskette that sounds really funny when you try to read it. I've gotten in the habit of trying to turn the diskette by hand if it sounds funny, and sometimes they won't turn freely -- or at all. What do you do then? You wash it.
Tell your client their disk is toast, but if you can destroy it, you may be able to recover some of the information. If they're comfortable with that, take your Swiss army knife or equivalent and very, very carefully pry the disk jacket apart, starting at the corners and carefully slitting the sides. You don't want the blade to come in contact with the platter inside. Open the jacket carefully and remove the platter inside.
Now clean the platter by running it under lots of cold water. No soap and definitely nothing abrasive. Pat dry with a (preferably lint-free) paper towel, then let it dry thoroughly. Once it's dry, put the platter into your empty repair jacket (you know, one of those old AOL disks, or a disk that toasted for some other reason that you've broken apart for just this purpose) and tape the jacket shut. Insert that disk into your floppy drive and see what happens. If you're really lucky, it'll work fine and you can copy the files to another diskette. If not, you can start running a disk repair back at section 1.
Zip disks are sort of like very large floppy diskettes. On a Macintosh, they are almost exactly the same, and you can use Norton Utilities on them just like a floppy disk even if it won't mount. On a DOS/Windows machine, however, you can't. The Iomega drivers are such that if the disk doesn't mount normally, it won't be accessible at all, and Norton Utilities can't do anything with it.
The other problem with Zip disks is what Iomega refers to as the "Click of Death". Simply put, when you insert a Zip disk into a drive it should click once and only once. The drive is homing the read/write heads (that's the click) then positioning them in the correct position to read data. If you get repeated clicks, then it's not reading some track information on the drive. It retries by rehoming the heads and positioning them again. This may simply be bad information (in which case you may be able to at least recover some of the files on the disk) or it may be bad track formatting (in which case you're probably stuck). If you only hear repeated clicks when you try to open a particular file, then grab the other files off the disk, reformat (if possible) and restore the files (or copy them to another disk.)
However, there is one instance in which the click of death will damage another drive (as COD has long been rumored to do). Before inserting the Zip disk in your machine, pull back the slider and carefully examine the edge of the disk. If you see a jagged nick or crack in the disk edge (and they can be very, very small!) do not attempt to recover the files on the disk. If you insert this disk into a drive, the read/write heads will catch on the jagged crack and be torn from their mountings. Once the heads have been torn loose, the drive will damage other disks in the same way. (Gee, a hardware virus!) So, inspect the disk very carefully before attempting to repair the disk or recover any files. The only thing Iomega will do under warranty is replace the disk; they can restore the data in many cases using a special drive, but it will cost you $250 (as of 1/1/2001). And they'll charge you for the tech support call, to boot. Which is why I don't like Zip disks.
If a Windows disk will mount, however, there are a couple of common problems that you can repair.
If a Zip disk with files open is ejected manually, and another Zip
disk inserted, when certain file write operations occur Windows will
write the directory of the original Zip disk over the directory of the
new one. When this happens, all the references in the directory
become wrong, and the files are lost. However, there will be
minimal damage to the file allocation table, and (except for the areas
that might have been overwritten during a file write) the files are
still on the disk. You can get them back like this:
REN *._DD *.DOC
to quickly rename all the files to something more useful.
If you have access to a Linux box with a Zip drive, there's an easier
way to figure out what type of files they are. Mount the disk and
open it in Konqueror. Konqueror will scan all the files (the
equivalent of the file * command) and find out what type they are.
(Because of this, clicking on the file opens the appropriate
application even if the filename doesn't have the right extension.)
The file types will be displayed in the "Detailed List" view,
and you can click on the "Type" header to sort the files by type.
Now make folders like "GIF Files", "Word Documents", etc. and
drag the files into them. Once you've sorted the files out by
type, get a shell prompt, change into the directories and use
for fn in
*._dd; do mv $fn $fn.doc; done
to add the appropriate extension to the end of the filename.
(Obviously, you'll want to change the extension as appropriate,
i.e., GIF for GIF files, html for HTML pages, etc.) Now Windows
will use the correct application to open it. Umount the disk,
eject it and take it back to a Windows machine to check your work.
If a file on a Zip disk refuses to copy, you may have a bad sector
in that file. Disk Doctor will normally find that and move it to
another location (if it can). If a Zip disk has a bad sector in
the directory, Windows will either refuse to display the directory of
the disk or (occasionally) just hang while trying. If that
happens, do this:
Yes, you can use Norton Utilities and many of the techniques described above on hard disks as well. You can certainly use the tricks for opening damaged Word and Excel documents, and Norton Disk Doctor will identify and repair minor problems with hard drives automatically. And, if you're looking for one file on a disk, you may be able to track it down (especially if it's small, text-only and you get extremely lucky). Beyond that, however, you're probably not going to want to work much with hard disks.
Why? Your clients can't afford it. The FAT on a hard
disk is huge. So are the directories. You'll have to hunt
for hours and hours to find the true location of a lost file, and it's
probably not going to be worth it. If they really, really need a
hard disk recovered, there are commercial places with the equipment and
software to do that a lot better than we can. Try http://www.drivelabs.com/, http://www.drive-experts.com/,http://www.corners.com/dataone/,
or the following Savvy
search. (Bear in mind that we've never worked with any of
these folks, so people are on their own here concerning quality. Caveat
emptor.)