One of the extremely powerful tool that come standard with Microsoft Windows XP PRO Operating System is called Group Policy Editor. Before I get into more details here the quick note on how to execute it:-
Go to START-RUN and enter gpedit.msc . Not so long ago, I had not idea that there could be extension like msc that would be executable. Well things have advanced a lot even though my mind still thinks in terms of COM,EXE,BAT file or INF files. Anyways,As soon as you enter gpedit.msc a window like the one shown below would pop up:

You are seeing the Microsoft XP's Group policy editor. There is quite a lot you can do with Group policy editor, e.g. change QoS setting or to disable or enable your ability to see and/or perform a wide variety of activities on your computer. I think I should give you some background on what is msc (Microsoft Common Console) file. I did a search on my computer and found out that there are 18 files that come by default on my Windows XP Professional operating system. Following snap shot lists the search results:

Resultant set of policy RSOP.MSC: This is another utility that you may use in combination with GPEDIT.MSC. You can see snap-shot of policy changes carried out in GPEDIT by executing RSOP afterwards. I will illustrate this in an example where I will show you practically how to speed up your INTERNET bandwidth and how to use both GPEDIT and RSOP screens. For now just look at the following snapshot to see what about link of RSOP looks like and says in Microsoft own words:

How to change QoS reservable bandwidth using GPEDIT.MSC ? Before I begin: Let me explain you what we are going to do. We are going to change QoS parameter from default 20% to 10%. You can change it to any number you like. Remember if the network card has a specific limit set on it in registry, this would have no impact on it.OK, so get ready and follow the steps.

Step 1: Log on as Administrator. I was earlier logged on as local user with Administrative priveledges but still that is not same as being logged on as Administrator.
Step 2: Go to START-RUN and enter GPEDIT.MSC (alternatively you can go into C:\WINDOWS\system32 and click on gpedit.msc microsoft common console document.
Step 3: Navigate to Local Computer Policy -> Computer Configuraton -> Administrative Templates -> Network -> QoS Packet Scheduler. Once there screen should some thing like as shown in the snapshot below.

Step 4: Look int the right pane and select Limit reservable bandwith. You would see a description that says default limits are 20% if not configured. If this is first time you have used GPEDIT, yours is not configured
Step 5: Double click on Limit reservable bandwidth. Following window would pop up. It is in this screen that you can enabled the limits and set to a number you want. I set the number to 10%

Step 6: OK out of the windows and GPEDIT.MSC. You are now all set.
Step 7: Go to START-RUN and enter RSOP.MSC (alternatively you can go into C:\WINDOWS\system32 and click on rsop.msc microsoft common console document.). You would see following window pop up

Step 8: Navigate to Console Root-> Administrator on (yourcomputername) - RSOP ->Computer Configuraton -> Administrative Templates -> Network -> QoS Packet Scheduler. Once there screen should some thing like as shown in the snapshot below..

Step 9: You would only see things that you have changd in GPEDIT.MSC. Since we only changed the limit reservable bandwidth, that all that is shown. Double clicking on this would show you what is the new value.

You can try out quite a few things. I am thinking of changing the values of time interval after which packets get scheduled for transmission.As shown in the snapshot below, it is controlled by value set in the Set timer resolution. At conceptual level I can bring it close to 0. I will try it out and let you all know my finds. Till than enjoy your life if you will and happy surfing.