Also looking into this as my mom works at NCSU, found this on one of the MS info/upgrade sites.
And while we don't recommend it, should you choose to upgrade your current PC from Windows XP or another operating system to Windows 7, we recommend that you get help with this process from your local computer service provider. You'll need to back up your current files and settings, perform a custom (clean) installation, and then reinstall your files, settings, and programs.
Says you can clean install.
http://www.microsoft.com/windows/windows-7/get/upgrade-advisor.aspx
Also check out this
http://www.microsoft.com/student/en/us/software/windows-7.aspx
look at the MSDN AA link and get a password from you school, its what jared51182 is talking about.
Free Win 7 pro DL if you go to almost any major school.