Hey There,
I would first off like to say welcome to the new world of custom built PCs, there is not better computer then the one you build yourself =).
So you are looking at building a gaming computer. Here are my pointers for you.
Processor: First off, do NOT go with a PD. They are outdated. If you want to go with Intel, you will want to go with a core 2 duo. The lowest end core 2 duo (the E6300) is only around a couple hundred bucks and is faster then the top of the line PD. At this point of time in the computer age, Intel has far more advantages over AMD processors other then AMD has a memory controller built into the processor (faster memory bandwidth) and that it uses hyper transport instead of front side bus (there can be a lot of arguments here, but I will leave it at that).
Recommended: Intel Core 2 Duo E6300
Motherboard: Do NOT go with micro-ATX. All the gaming boards are ATX boards and for good reasons. So you will not be able to use a small form factor case. You will not find any good chipsets for gaming in a micro-atx board. Also, make sure your chipset is NOT sis. You will want to get an SLI board so you can have the option down the road to add another graphics card to pair up with yours for more video power. Do research on the motherboard before you buy it and make sure it had good reviews.
Recommended: EVGA 122-CK-NF68-AR (nForce 680i SLI 775)
RAM: Use name brand memory. None of my distributors carry Patriot memory. I am not sure on how good their warranty service is. Stick with Corsair or Kingston. Might want to check out Super Talent maybe...They have lifetime warranty and I read some good reviews on their gaming ram. If using Core 2 Duo processor you want DDR2 800 or higher memory. Even if the motherboard doesn't support higher then ddr2 800, you will want to get a higher speed because then you know you can overclock the memory at a higher speed then 800 a lot easier. Make sure the memory you get has low latency. Such as CL4 instead of CL5. The lower the CL number the faster the ram will be but you will have to overclock the ram first to achieve this speed. Also, you might want to look into getting at least 2 GB especially when Windows Vista becomes a standard.
Recommended: Kingston KHX8000D2K2/1G
Video Card: The 7600 GT is fine. I personally use it and haven't came across a game where you couldn't play it with everything on HIGH settings. You might want to look into the 7900 GT's now that the prices are coming down on those because of the new 8000 series graphic cards that came out.
Recommended: EVGA 256-P2-N554-AX (7600 GT 256 MB)
Power Supply: Antec is usually your best bet. They have the biggest name and better power efficiency then most other companies in their better power supplies. You will want one that supports SLI.
Recommended: Antec TruePower Trio 550
Hard Drive: Your fine. SATA is the only way to go now and days. I recommend going with Western Digital and Seagate. Don't use the Hitachi DeathStars!
Hope this gives you a better idea!
Jesse