Building/Buying a gaming PC

Alright. I'm back with a refined build. Thanks for the recommendations guys. Oh, and I can't reuse my old CD/DVD ROM anymore. Meh.

So, here it is.

CPU: AMD Athlon II X4 635 $102.99
Mobo: MSI 870-G45 AM3 AMD 870 ATX AMD Motherboard $71.99
RAM: G.SKILL ECO Series 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1600 $102.99
Case: COOLER MASTER RC-692-KKN2 CM690 II Advanced $99.99 (with $10.00 instant rebate: $89.99)
GPU: EVGA 01G-P3-1370-TR GeForce GTX 460 $229.99
PSU: Antec TruePower New TP-650 650W Continuous Power ATX12V V2.3 $135.49 (with $31.00 instant rebate $104.49)
HDD: Western Digital Caviar Green WD10EARS 1TB 5400 RPM $71.99
CD/DVD ROM: SONY Black 18X DVD-ROM 48X CD-ROM SATA DVD $18.99
OS: Microsoft Windows 7 Home Premium English $224.99 (with $19.00 instant rebate $205.99)

Subtotal: $999.41

So, I got a different OS now. It's not OEM. So, I'm assuming I can use it multiple times. It costs $200 though. I really have no idea if this is standard. I'm pretty sure it's 64-bit. It doesn't say in the name, but looking through the specs it said something about 64-bit. Could someone confirm this?

So yeah. that's my refined build. Comments?