Assuming you have a case and peripherals:

Motherboard: http://www.newegg.com/Product/Produc...82E16813128357 - $53
CPU: http://www.newegg.com/Product/Produc...82E16819116072 - $63
4GB RAM: http://www.newegg.com/Product/Produc...82E16820231122 - $54
Video Card: http://www.newegg.com/Product/Produc...82E16814130339 - $130
Power Supply: http://www.newegg.com/Product/Produc...82E16817371015 - $80
HDD:
DVD Drive - http://www.newegg.com/Product/Produc...82E16827151187 - $30

Grand total ~ $410. That's assuming you don't have DDR2, a decent PSU, or a DVD Drive. It's a pretty limited system but you it could fair pretty well I'd think.

Kill's setup is pretty nice.