So let's see, you need a working computer for around $700. Not bad.
I know an online configurator that will offer the following for $835 shipped to your house, working, OS installed, etc.
CoolerMaster Elite 310 Case
600W Power Supply
AMD Phenom II X4 945 (3.0GHz QUAD CORE)
4GB DDR3 Corsair RAM @ 1600MHz
ATI Radeon 5770 (Direct X 11!)
320GB Seagate Barracuda Hard Drive
LG 22X CD/DVD Burner
Windows 7 Installed
That's... not bad for $835. Trust me! You can add a Monitor for $100 ~
So t3tr1s, you want to build your brother a computer and I'm here to help. $700~ you say? Let's go to NewEgg shall we? I'll post again in 10-15 Mins!
If worst comes to worst t3tr1s, I can give you a free NVIDIA 7900GT from EVGA (supports HD and stuff). If you still want a video card, get a cheap ATI Radeon HD 5450 for $35 (It has DirectX 11 Support!)
So, our Grand Total now is: $628.36, $608.36 after Mail-In Rebates! This gives us some good breathing room for a Monitor, Keyboard, Mouse, and Speakers. My suggestions:
If we add that to our cart, our Grand Total is: 803.79, 783.79 after Mail-In Rebates!
Grrr! I failed you t3tr1s! I got you a lot of name-trusted brands and pound-for-pound parts. I was aiming for more like $730 If you want, I can actually down-grade the CPU a little bit if your brother isn't going to be doing hard-core stuff on it. That might suit the wallet better
Grand Total after Shipping + Taxes: $736.38, $716.38 after Mail-In Rebates!
You have options t3tr1s! I can get you an AMD Athlon II X4 @ 2.8 GHz (QUAD CORE), or 2.6GHz for (+$20/+$10) if you prefer a Quad-Core to a Dual-Core.
If you really want to be daring and nerdy, buy the motherboard seperately and buy this AMD Phenom II X2 550 @ 3.1 GHz (DUAL CORE). It will cost you about (+$30), but this BLACK EDITION of AMD's Phenom has two un-locked cores. That's right, you can make this a Quad-Core if you know how. There are guides online on how to do it. If this seems too daunting, go with what I suggested above. You'll be more than happy.