64bit machine requires windows 7 64
are you saying you can't run a 32 bit operating system with a 64 bit CPU :questionm
you can't really compare OS's for speed unless all of the hardware is Exactly the same on all systems.
XP 64 bit supports as much ram as 7 64 bit
Basically, I need something that can run contiounsly. I will be doing alot of CAD work, hard programming, and 3D rendering..