Ok, so I'm in a bit of a bind, and I'm hoping someone can give me some simple advice. I bought an old HP Pavilion a6400f PC for my 8-yo daughter just so she can play one of her favorite games. First obstacle, I needed to upgrade nearly everything except for the mobo. Ok, no big deal - still cheaper for me in the long run. I've built my own A/V rig in the past, so I figured it'd be fun to take this on. Researched everything - the GPU, RAM, CPU, PSU - to make sure it was all compatible, etc. However, the final obstacle that I haven't been able to figure out is what I should do about the OS in order to upgrade it to 64-bit. Like I said, this was cheap (estate sale), and there were no discs that came with it. So, I'm stuck with a 32-bit Vista OS. My question.... - Should I upgrade to 64-bit OS or 7? - If 64-bit Vista, how??? I've googled it and I'm a little unclear on whether I can do this for free. - If 7, my A/V rig has 64-bit 7 Pro, but I doubt I'll be 'allowed' to use that license to install it on a second PC. Just trying to get by spending as little $$ as possible Thanks for your time!