Hi! I have Hitman: Absolution and Microsoft Office 2010, that both need Windows 7. Luckily, I have an official Windows 7 install disc for both 32 and 64. Now, backing up all my qaqa on 4.7 GB dvd discs would be a hassle, and that would be what I'm looking at because there is only one hard drive. My question: What are the downsides to just installing Windows 7 64 bit over Windows XP 64 bit, rather than backup files -> reformat -> clean install?