Thanks for all the info. My computer was purchased from a private person. It has an AMD Athlon XP 2000 1.66 GHZ Processor, 511 mb ram. The system is 32 bit. Hard drive is 37.2 gb with 10.2 gb free. It is Windows Vista Ultimate 6.0.5600 Build 5600 operating system. It did not come with a CD for Windows. So I can get a Windows Basic or Ultimate upgrade and install it?? Do I have to do a clean install?? If I do, how can I back up my files?? Thanks again. I am sorry to ask so many questions but I am new at trying to install an operating system.