Here is my recommended system...
CPU- AMD Athlon 64 3500+...$272
Motherboard- ASUS A8V Deluxe...$129
RAM- 1GB (2x512MB) Corsair XMS PC3200...$204.27
Hard Drive- 120GB Western Digital IDE 7200 RPM...$82
Video Card- eVGA nVidia 6800GT...$399
Optical Drive- DVD/CD-RW Combo 52x32x52x16...$40
Case- Thermaltake XaserV w/ Antec 480watt psu...$155
Monitor- NEC 17" Flat Screen...$155
Speakers- Logitech X-120 2.0...$23
Keyboard- Aopen black keyboard...$8
Mouse- Microsoft Optical Mouse...$18
Ethernet Card- 3com 10/100 Ethernet Card...$25
Operating System- Windows XP Home OEM...$91
I don't know if these prices are all the cheapest, but I did this all on newegg.com because it's easier that way
Your total comes to...$1601.27.
If anyone can think of any system components that I'm missing, post it. Otherwise, I think that would be a great system for gaming or anything else for that matter. Before I get roasted, I realize that the speakers, keyboard, and monitor are not top of the line, but I tried to focus the majority of the money on the components that would affect gameplay, such as the CPU and video card.