Build me a new computer!

[supremespleen]

So, I kind of want to get a new computer going. My current is about four years old and just doesn't cut it anymore and it is set up that upgrading it is kind of a pain. So, if I were to go to newegg and buy all new stuff, what would I get? I have no experience with PC scratch building. I'm looking to spend about 600-900, if possible. I have XP stuff from my last PC, so I don't need an OS.
I'm also going to be getting a job to pay for this, so it better be worth it :P My goal is to be able to play TF2 on max.

Thanks for your help.

[Lord.Roderick.i]

I made a Thread about getting XPS or Alienware, that diverged into building a new PC here:
http://www.ocremix.org/forums/showthread.php?t=11694
And my solution was getting the PC Building Bible
Helped me a lot.
It should help you to get started.