If you need to upgrade from Windows XP to Windows 7 then you probably know there is no upgrade path - only a clean install. Have you thought about using the Windows Easy Transfer tool to help migrate your files and settings?
Sometimes we need to back up files of PCs away from our WHS. Microsoft makes a great utility just for this purpose. This utility walk through is for XP but there are similar versions of this utility for Vista and Windows 7.
I'm going to build a new Windows 7 installation for my home workstation in a VirtualBox setup, so that I can continue to use Windows Vista, with (almost) no downtime.