Can i run Windows Vista 64-bit?

Yes you most certainly can. Your Intel Core 2 Duo E8500 and other hardware support 64bit instructions and will work very effectively with any x86 coded 64bit operating system. A little bonus is that Vista 64 will recognize all 4GB of your RAM while Vista 32bit has a 3.5GB limit. You will definately be getting the most out of your PC going with 64.