You can make a pretty nice desktop for $450.....Ummm...off of memory:
AMD Athlon 64X2 5400+ (2.8 ghz) = $87.00
*EVGA (lifetime warranty) 8800GT = $129.99 (also free Crysis game!)
*2GB Corsair RAM (lifetime warranty) = $34.00
Standard DVD Drive = $20-$30
250 GB Western Digital HDD = $54.99
*Antec 900 case = $79.99
Any decent motherboard = $79.99
(Monitor, keyboard, mouse not included (assuming you already have those) )
*NOTE* Any product with a '*' has a mail in rebate to achieve that price!
Check these items on Newegg if you're not sure...
EDIT: OK this rig is ~ $536...(Check EDIT 2)
EDIT: Darn, I forgot the PSU...That'll add another $50 or so...







