I recommend for the RAM, Corsair XMS2 PC26400, but other brands such as Crucial, OCZ, G.Skill and kingston are also very good. As for the amount, if you're going to be playing new games such as Crysis, Bioshock etc, 3gigs or more will make a huge difference. I used to play Crysis with 2gigs and I used to get a lot of lag, now I have 4gigs and a nice smooth frame rate. If I monitor my RAM usage in these games, I'm using 2.5gigs plus, so 4gigs is definitely worth it. For the PSU, make sure you get a good brand, cheap crap doesn't produce the power they're supposed to and they could damage other components when they fail, which they often do. Get something 500W+ and with 30A+ on the 12V rail. If it has dual 12V rails, even better. And for the GPU, like everyone else says, go with the 8800GT 512MB if you play at more than 1280x1024, if you don't then the 256MB version is fine. Another card to have a look at is the ATI Radeon HD 3870. A bit cheaper but the 8800GT outperforms it by about 10%, still a great card though. Hope this helps.
and when i put it together, do i just install all the hardware and then install windows and the drivers after it boots up? thanks for any help you guys can give me.
You must install all the hardware first, then boot the PC, put the windows disc into the drive and press reset and then if you are prompted to press a key to boot from CD/DVD, do so and follow the instructions.