hey i have a hp dc7800 and has windows xp pro installed on it right now but on the tower, its got the vista sticker in front and on the side has the sticker with the product key and all so im wondering if i can just find a vista business download and then just use that product key to re-download, becasue i think the previous owner installed windows pro, but even when i go to recovery xp pro i the only one available,but since i have the product key means its already pruchased. so the question is if i can re download it where can i find the download online? and how do i know if im 32 or 64bit? thanks