Windows 7 Ultimate
(My cousin goes to Indiana University where they sell Windows 7 Ultimate for $20. She owes me a favor. And I basically saved $200+. Epic win.)
Oh and some zip ties to help manage cables. I'm also salvaging 2 hard drives and a DVD drive to help save some money. Altogether, I spent about $770 (I had a $30 rebate from the graphics card) plus this build costed me a favor.
get intel i5 2500k cpu and a cooler master hyper 212 evo cpu cooler. instead of asus get a asrock z68 extreme3 mobo and id get g.skill ram instead of corsair, although they have good ram. and id get a rosewill capstone-550w psu rather than that corsair, for a case you should get a three hudred illusion black steel case, and the best place to buy parts is newegg, microcenter is good too but not better than newegg (unless there is a microcenter store near you)