Hello, I just have a question about how the Windows 7 upgrade works. I'm being offered Windows 7 Business Upgrade. I do really want to upgrade to Windows 7 from my current Windows XP. The problem is that I recently wiped my Windows drive on my Mac because it was virus-ridden. Do I have to install Windows XP to be able to upgrade to Windows 7 Business, or when I try to install Windows 7 will it just ask to insert my XP Install disc and ask for my license? Thanks. Also, should I get 32 or 64 bit?