I think everyone is missing the point here. The problem is not about saving some money it is about saving time! I've been backing up my data for 2 weeks now and still have not completed the process. I have years of installed, registered, and setup applications that I downloaded from websites all over the internet. Trying to find all the downloads again, then reinstalling and setting up again will take months! I did not upgrade to Vista because of all the nightmare stories about Vista and knowing many of my apps would not run on Vista. I now have Windows 7 but will take months before I can install and use it. Just think if your in IT and have to do this on lots of computers! Since you can upgrade XP to Vista and Vista to Windows 7, Microsoft should let me enter my valid Windows 7 product key to download Vista so I can upgrade XP to Vista and then upgrade Vista to Windows 7. It is not XP users fault that Vista was so bad that we all waited for Windows 7, it is Microsoft's fault. By not making XP upgrade to Windows 7 is going to make Windows 7 a failure just like Vista was except for different reasons. I really just want my money back for Windows 7 so I can go buy my first MAC.
Quite frankly, your data should be off the system drive in the first place. If it was, it simply wouldn't be necessary to back it up, because it wouldn't matter which version of Windows was installed.
Any programs that you downloaded should have had the setup files burned to disc before there was any attempt made at installing them. Plus writing the product keys down and keeping multiple copies in multiple safe places.
Plan "B" would have involved buying an using a disc imaging program such as, Acronis "True Image". Oh yeah, and installing and using it.
And Vista will run XP programs, it will set the compatibility mode to XP automatically, or you can set it manually.
And BTW, Vista isn't that bad, it just isn't that good, there is a difference.
And good luck with that Mac Yo, especially with finding "software all over the internet" to run on it!
And I think that if we all, "missed the point", that you missed it right along with us.