Tell us where you live, the site of parts where you can order from, what it has to include or exclude (monitor/keyboard/mouse/speakers/etc).
No offense or anything, but judging from how you talk about what you are looking for, I would not suggest building your own computer. I know someone like you that ended up throwing 800 dollars down the toilet when he didn't discharge himself before going to build the computer. For you I would suggest looking at: http://www.ibuypower.com/ and http://www.cyberpowerpc.com/ The main things you would want for a good gaming PC would be: at least 2 Gigs RAM at least a 200 GB hard drive at least a 7300 video card at least a 2.5 ghz processor
Go for 2048mb RAM (2gb), DDR2, highest speed possible Mobo is kinda hit-miss, post the mobo you want, we can check it out Video card : You'd want at least a nvidia geforce 7900GT (256mb) Sound Card : Audigy, whatever you want, as long as it isnt a low-profile, those usually suck Proccesor : Core 2 Duo definately, probably a 6600 would be good 'nuf I really need specifics to build one though, sites etc.
7300s suck, 7600GTs are borderline acceptable. GHz isn't a measure fo processor performance. a C2d(Core 2 duo) at 1.83GHz can outgame a 3.73GHz Pentium eXtreme Edition.
