I know a lot of you guys have way more experience with this than I do, so what parts should I get for a gaming rig?
- I'd like to keep it under $1000
- I already have a copy of Windows 7, so that'll save some money
- Don't worry about a case, I can reuse an old one or build my own.
If I forgot any important details, I know you won't be afraid to let me know. :-P
Thanks!

Maybe a place to start and here . . . =)

There are a number of other things you forgot to mention. Are you keeping the monitor, speakers, keyboard and mouse? What PSU do you have in the case? What form factor is the case you're keeping? Are you keeping DVD and hard drives?

You should be able to get a Core i7, 6GB of ram and a GTX465 or 470, a hard drive and a decent soundcard for under a grand

Then he can sell his microwave too. :P

Wow, you're actually capable of unconcealed, plain funny comments! I shall cherish this moment for the years to come.

i7 in a computer under a grand? What kind of world do you people live in?

My brother wanted an i7 laptop . . got this one a few weeks ago. Seems they offer i5 with Win 7 Pro and i7's with Win 7 Home. He got the Anytime Upgrade ($79) to Win 7 Pro and had just under a thou in it. Playing all games installed so far . . . =)

I actually need (want) a new proc and the i7 excites me in multiple body parts, but it's still expensive as hell. I'm totally up for the 965 or 960 (meh, whatever) but then I need DDR3 RAM, a new motherboard, and God forbid, a bigger power supply.

Well don't be too down on the clock speed of the lower model i7s, the overclock potential is pretty hefty. Hell to give you an idea of the ambition of my system, the maximum clock multiplier can apparently give me 12.3GHz, I'm obviously not going to DO it since I have no doubt it wouldn't be stable and because I prefer it when my power bill is under 4 figures

Hmm personally I'd replace the 265 with a HD5xxx card, NVIDIA cards always seem to run at melting point when I use them..

Afre ythe HD5xxx's DX11 compatible? That was the thing that I was looking for, maximum compatibility with minimum price

Thank you all for the help so far!
@Alpha: I like your build a lot, but do I really need a sound card? I'm not exactly an audiophile.
@Navagon: Ooo, good point, I should be able to get my hands on a monitor, but that's not certain... Speakers, keyboard, and mouse I should be good on; I'd like new ones, but the budget's pretty tight right now. I'm pretty sure I'll need a new PSU, maybe I've got one good enough, but none of the computers I'd be pulling parts from were designed for gaming, so I'd be surprised. If the case fits the parts, great, but I'm okay with building my own case if necessary. I have DVD drives, but I will need a new hard drive.

The guy over at Hardware-Revolution really does his research and comes up with some very nice builds; he also keeps them up to date and does very thorough monthly run-downs of processors and graphics cards.
He's got builds ranging from $400 to $2000 in the gaming category (fewer in the other categories, eg workstations)
http://www.hardware-revolution.com/computer-systems/gaming-pc/
The $1000 machine is here:
http://www.hardware-revolution.com/hardware-revolutions-1000-gaming-build-version-2-0/
(The $850 is the most recent complete build update, the $1000 is from January)
And all the builds have proposed alternatives/upgrades and detailed per-part explanations, as well as comments sections (to which he responds!).
Also, read this article on power supplies:
http://www.hardware-revolution.com/warning-6-surefire-ways-of-blowing-up-your-computer-due-to-an-inadequate-power-supply/
I recently used one of his builds as the basis for a machine I built for a friend, and after doing some specific research ended up changing it very little.