Wow... this got way offtopic...
Anyways, here is what you requested.....
CPU -
AMD Athlon 64 3200+ - $99
Mobo -
DFI RS482 INFINITY - $88 - (onboard LAN, sound, VGA & DVI)
Case -
Antec Minuet 300 - $77 - (with PSU)
You didn't mention these, but I put them in here anyways...
Memory -
CORSAIR XMS 1GB (2 x 512MB) DDR400 - $126
Optical -
LITE-ON Black DVD+/-RW - $40
Hard Drive -
Seagate Barracuda 7200.9 - $66
With everything I linked, it is $496 before shipping... It would be just overbudget, so you could go with 512MB ram instead of 1 Gig, or a smaller HDD... Also, the motherboard has onboard video, and a PCI Express x16 slot if you plan to upgrade to better graphics in the future.