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 $760 (I had a $30 rebate from the graphics card) plus this build costed me a favor.
It's a good start but FX is not good. There's way too many installation errors and software problems associated with it. Go Intel, or if you want to stick with AMD go with the 960T, or 970T.
Speakers and things like zip ties and wifi adapters are so cheap that they can be an afterthought. Get those last and put the money into getting the best hardware you can get. Most of what you have is certainly not bad but you'd definitely be wise to reconsider the FX-4100.