My favorite web site for shopping pretty much any thing is http://www.ebay.com also http://www.amazon.com, http://www.newegg.com, and http://www.zipzoomfly.com. 

NEW! Now I have a special service for building custom computers that will last and be almost half the cost of a store bought computer! You can chose  exactly what you want in it which can make the computer price go down depending on the components. To save some money I buy AMD processors instead of Intel because they tend to be cheaper. They also have QuantiSpeed on the CPU witch  quadruples the speed of the possessor like a 2.0 GHz w/ QuantiSpeed comes out to be a 2400+. Also  If your wondering the equivalent of the Intel Pentium 4 is a AMD Athlon XP. I have one and they come with a three year warranty only with retail boxes not OEM.

To see what I bought for my last computer I built look below. The total is at the bottom.

  PC Case $35.00 +SH

Floppy Cable $1.25 +SH

IDE cable $0.99 +SH

256MB video card $73.00 +SH

Floppy Drive $6.88 +SH

Monitor $140.00 +SH (not actual monitor I already had one)

Network card $15.00 +SH

256MB x2 RAM $220.00 +SH

   AMD Athlon XP 2400+ CPU $89.00 +SH

GIGABYTE GA-7ZMMH motherboard $26.99

DVD Burner $120 +SH

Western Digital 80GB 7200RPM hard drive $62.00 +SH

Mouse $2.50 +SH

Keyboard $4.00 +SH 

Windows XP Professional full version $146.00 +SH

Total $942.61 plus Shipping and Handling 

Total without monitor, mouse, operating system, or keyboard $650.11 plus Shipping and Handling