Why not use the W7 Easy Transfer Wizard to save your files and settings, then do a clean install, it's easier and a better way to go. You will need to reinstall your programs.
To use the W7 Easy Transfer Wizard:
Browse to the DVD drive on your computer and click migsetup.exe in the Support\Migwiz directory.
Boot from the W7 dvd and choose custom install for a clean instalation.