New build finished! Now want some opinions on the OS

[tomhrxbfg2]

Hi guys, so I just completed my first build in like 4 hours...Used really cheap parts and right now I need an OS. I am using win8 preview now but I am planning to switch to 7. I can get the win 7 pro upgrade for $65 (student price), win 2008 server R2 for free (being a student), or stay with win8 until it expires and buy the new win8 for $40.

Parts used:
Phenom II 965 $90
8G RAM $35
Asrock 760 mobo $54
Corsair 500W PSU $25
Fractal 3000 case $40
DVD burner $15
reused laptop hard drive
Total $259
Hopefully I could add a video card and ssd later

 

[rdc85]

Make sure it's all 64-bit.... I'm leaning towards win 7 pro