First Computer Build

Specs:
Case: $150
Antec P182 Gun Metal Black 0.8mm cold rolled steel ATX Mid Tower Computer Case – Retail
Motherboard: $180
DFI LANPARTY DK X38-T2R LGA 775 Intel X38 ATX Intel Motherboard - Retail
Graphical Processing Unit: $330 – $30 rebate
EVGA 896-P3-1260-AR GeForce GTX 260 896MB 448-bit GDDR3 PCI Express 2.0 x16 HDCP Ready SLI Supported Video Card - Retail
CPU: $190
Intel Core 2 Duo E8400 Wolfdale 3.0GHz LGA 775 65W Dual-Core Processor Model BX80570E8400 - Retail
RAM: $109 – $30
CORSAIR XMS2 DHX 4GB (2 x 2GB) 240-Pin DDR2 SDRAM DDR2 800 (PC2 6400) Dual Channel Kit Desktop Memory - Retail

Storage: $90
Western Digital Caviar SE16 WD6400AAKS 640GB 7200 RPM SATA 3.0Gb/s Hard Drive - OEM
Operating System: $110
Microsoft Windows Vista Home Premium SP1 64-bit English for System Builders 1pk DSP OEI DVD - OEM
Thermal Compound: $7
ARCTIC COOLING MX-2 Thermal Compound - Retail
Cooling System: $37 - $10 rebate + $7
XIGMATEK HDT-S1283 120mm Rifle CPU Cooler - Retail
XIGMATEK ACK-I7751 Retention Bracket – Retail
Optical Drive: $28
Lite-ON 20x DVD+R Sata - Retail

Power Supply Unit: $125
SILVERSTONE ST70F 700W ATX12V / EPS12V Power Supply 100 - 240 V RoHS, CE, cUL, FCC, TUV - Retail

Subtotal: $1,362.89
-$70.00 (rebate)
=
Total: $1292.89

These are the specs that I've initially drafted up. I plan to use the integrated sound on the mobo until I can decide on a soundcard when I have more money to play around with. I've sent it to a few friends and some have been recommending a 32-bit OS while others recommend a 64-bit OS. I don't use the computer for much more than FRAPS, Age of Conan, Itunes, Trillian, and Firefox. So I'm trying to optimize my gaming performance as priority. I don't plan to do intensive video encoding or use the computer as a server. I hear a lot of confusion about 64-bit os drivers. Then I'm also in the dilemma of XP 32-bit, XP 64-bit, Vista 32-bit, and Vista 64-bit. I was wondering if anyone had suggestions about the computer specifications itself (maybe the sizes dont match up, cooling system isn't strong enough, PSU is too weak, etc.). I'm pretty satisfied with the research I've done for my first self-built computer. But I'm also looking for any advice anyone has to offer. Thanks for your time!

Thanks, do you have any opinions on the Operating System?

YES~!!! Somebody getting DFI and not Asus
+1 for 4870.
+1 Corsair 750TX PSU
+1 P182

You picked out pretty solid parts for a first time builder. I'm impressed that you didn't just copy everybody else's same old same old. About the video card, the 4870 is a much smarter choice than the GTX 260 based on available benchmarks. About the powersupply, Silverstone makes great ones, but Corsair has a better deal on a comparable PSU in terms of features and reputation.

Besides what I've mentioned, your system is killer.