I am attempting to build a computer particularly for gaming purposes for around 1,000 dollarsish. So I've been doing some research and I've come up with a basic plan I have.

CPU: Intel Core 2 Duo E8500 Wolfdale 3.16GHz LGA 775 65W Dual-Core Processor Model BX80570E8500 - Retail - I believe this is a decent choice for what I'm attempting

Mobo: BIOSTAR TPower I45 LGA 775 Intel P45 ATX Intel Motherboard - Retail - I picked this one mainly because of its compatibility with my cpu and its good reviews. Is Biostar a good brand?

Case: NZXT Apollo Black SECC Steel Chassis ATX Mid Tower Computer Case - Retail - this one looks cool. Oh and according to a number of reviews it is quiet, which is something I'm looking for

Memory: G.SKILL 4GB (2 x 2GB) 240-Pin DDR2 SDRAM DDR2 1066 (PC2 8500) Dual Channel Kit Desktop Memory Model F2-8500CL5D-4GBPK - Retail - I think this is enough and fast enough for most games? I figure in the future i can always add or upgrade if I feel the need.

Video Card: SAPPHIRE 100225L Radeon HD 3870 512MB 256-bit GDDR4 PCI Express 2.0 x16 HDCP Ready CrossFire Supported Video Card - Retail - Okay so this is where I'm having a bit of trouble...is this a decent choice? or is it incompatible - I think it would fit into my mobo =/

HDD: Western Digital Caviar SE16 WD6400AAKS 640GB 7200 RPM SATA 3.0Gb/s Hard Drive - OEM - I like space? Idk

Optical Drive: SAMSUNG 22X DVD Burner Black SATA Model SH-S223F - OEM

OS: I was thinking Vista 64-bit home. Cause Idk, its not that bad is it - or just windows xp it up?

Few questions: (1) Will I need a power supply? (2) Will I need an external cooling system? - I may overclock.

Thanks Sammy for referring me to the other post it helped me realize my video card was old. Also that my mobo was not what I was looking for.

So I have been considering this card-
SAPPHIRE 100259-1GL Radeon HD 4870 1GB 256-bit GDDR5 PCI Express 2.0 x16 HDCP Ready CrossFire Supported Video Card - Retail

and this Mobo - ASUS P5Q Pro LGA 775 Intel P45 ATX Intel Motherboard - Retail

also I looked to get a power supply,

PC Power & Cooling S75QB 750W ATX12V / EPS12V SLI NVIDIA SLI Certified (Dual 8800 GTX and below) CrossFire Ready 80 PLUS Certified Active PFC Power Supply - Retail

750W seemed on the excessive side but it is a pretty good deal.

> "OS: I was thinking Vista 64-bit home. Cause Idk, its not that bad is it - or just windows xp it up?"
Indeed, it's not bad. In back many of us on this forum think Windows Vista is a good OS and better then Windows XP.
One thing to keep in mind though, Windows Vista comes in two versions, 32-bit and 64-bit.
The 32-bit version can't use RAM above about 3.2GB.
The 64-bit version can use RAM above 3.2GB but only with 64-bit programs, you can run 32-bit programs but not 16-bit programs (which shouldn't be a problem for any software made in the last few years as it's all either 32-bit or 64-bit) and you can only use 64-bit drivers (which are usually available for recent hardware).

good choice in both videocard and psu (enough power for future upgrade)
HOWEVER like i mentioned in the other thread, if you plan to buy another videocard in the future to crossfire, then radeon is NOT the way to go. ATI has many crossfire driver problems. Its a great videocard on its own, so if you plan to stick with only one card, then its a great choice but two in crossfire will most likely give you grief.

This is what I have come up with all your help. Anything like absurd?

Case: Antec Twelve Hundred Black Steel ATX Full Tower Computer Case
CPU: Intel Core 2 Duo E8500 Wolfdale 3.16GHz LGA 775 65W Dual-Core Processor Model BX80570E8500
Motherboard: EVGA 132-CK-NF78-A1 LGA 775 NVIDIA nForce 780i SLI ATX Intel Motherboard
Memory: G.SKILL 4GB (2 x 2GB) 240-Pin DDR2 SDRAM DDR2 1066 (PC2 8500) Dual Channel Kit Desktop Memory
Video Card: ASUS ENGTX260 TOP/HTDI/896M GeForce GTX 260 896MB 448-bit GDDR3 PCI Express 2.0 x16 HDCP Ready SLI Supported Video Card
Harddrive: Western Digital Caviar SE16 WD6400AAKS 640GB 7200 RPM SATA 3.0Gb/s Hard Drive
Power supply: PC Power & Cooling S75QB 750W ATX12V / EPS12V SLI NVIDIA SLI Certified (Dual 8800 GTX and below) CrossFire Ready 80 PLUS Certified Active PFC Power Supply
Optic Drive: SAMSUNG 22X DVD Burner Black SATA Model SH-S223F
OS - 64bit vista

> "which from what I can tell shouldn't be a problem as long as I don't want to install any ancient software?"
Correct.

Before you purchase anything check these combo deals from newegg.
If you decided to take my advice on the videocard, you can take this deal, and save $65! not only will this deal make the EVGA card cheaper than the Asus you picked but it also has better performance!I highly recommend!
However if you still want the Asus card then theres this deal.