Could use some helping putting a system together...

Hey, I'm new around here obviously but I saw a few threads and saw that people were very kind and helpful to those with little knowledge of PC hardware and such... So I figured I'd try it out...

Basically I've built... or aided in the building... of one rig before, my own. I say aided because it was basically all my friend who has since moved away... I'm looking to build another because mine got scrapped after a party a week or so ago (Yeah... It sucked...). Anyway I sort of followed along when my current rig was built but I'm not yet confident enough In my ability to pick out the correct parts for what I need, or want, rather. Most of my usage is to play MMO's like WoW online so That is the main reason I need the new pc, and the main thing I want it to succeed at. Nothing else really stands out as far as what I need it to do...

Here's the catch... I'm 18, just recently graduated Highschool, and currently am without a job (Damn economy... Nobody is hiring...) Anyway, This obviously puts my budget rather low... I am thinking that I could scratch up 700-900 dollars in the next few weeks so I am saying 900 is the most I'd be willing to spend, most meaning I'd prefer if I could keep it below that price, but I know these things can get expensive and I'm not one to just throw together a pos computer that JUST works.  

Anyway I'd love it if anyone with experience could help me pick out some components, I don't need a monitor, keyboard, or mouse. Not too worried about high-end sound cards, and having a huge hard drive really doesn't tickle my fancy, what I'm most concerned about is having a great processor and an even better Graphics card (Yeah, the two most expensive things, right? lol). Anyway If anybody could help me out here that'd be great, I'm surfing Newegg right now Like I said I'm just not sure if I know what I want, and I'm sure that I'll end up going over what I need or not getting enough...

ANY help at all is MUCH appreciated, Thanks so much!!!

Joe

P.S. I'd also like to know what everyone's thoughts are on prebuilt name brand systems, I know a lot of people frown upon these for gaming and even general use... But I was at best buy today (the CHEAPEST place on earth, right?) and I saw http://www.bestbuy.com/site/olspage.jsp?skuId=9366633&t...

It's 750 dollars but from what I see anyway it could work for me... But I know there will probably be stuff someone will point out that I didn't see, anyway Any help is much appreciated   thanks.