My friend asked me to build him a computer. Here's what I came up with:

1x GeForce 9500 GT 512MB DDR2 PCI-E 2.0 http://stores.tomshardware.com/sea [...] t/sv=title
1x Intel Core 2 Quad Q6600 Processor http://stores.tomshardware.com/sea [...] t/sv=title
1x eVGA nForce 650i Ultra 775 T1 http://stores.tomshardware.com/sea [...] roduct_tab
4x Kingston 1GB PC4200 DDR2 SODIMM Memory http://stores.tomshardware.com/sea [...] t/sv=title
1x Caviar SE WD1600AAJS 160GB Hard Drive http://stores.tomshardware.com/sea [...] t/sv=title
1x COOLER MASTER Real Power Pro RS850EMBA 850W Power Supply http://stores.tomshardware.com/sea [...] t/sv=title
1x Cooler Master Centurion 5 Blue Mid Tower http://stores.tomshardware.com/rat [...] /sv=review
1x Lite-On LH-20A1S-15 Black Dual Layer DVD±RW Writer http://stores.tomshardware.com/sea [...] t/sv=title
1x Microsoft Windows Vista Home Premium SP1 64-bit English for System Builders 1pk DSP OEI DVD - OEM http://www.newegg.com/Product/Prod [...] 6832116488

I built this machine to run games. He said he wanted to run crysis well. If this does not work please tell me and explain why. I am pretty sure I covered everything.

The psu is overkill. Dumb it down to Corsair 450W or better yet, a Sonata with a quality psu:

http://www.newegg.com/Product/Prod [...] tec+sonata

The 9500GT is a weak gpu. If you look around, you may find 8800GT/9600GT for about the same price after rebate. Either of the latter ones is good for gaming. Especially if he wants to run crysis. Slow gpu will work, but the game may look like a slide show.