"You'll need to move your files off of your PC before you install Windows 7"

I just did another install of Windows 7 on a machine, where I took the option for a fresh install (as opposed to an "upgrade").

So long as you don't take the option to re-partition/re-format your drive, all of your old folders stay intact...and your existing WINDOWS and PROGRAM FILES are moved to an OLD.001 folder structure. I have no clue why they say what they say (maybe to get people to do backups anyway?), but so long as the drive isn't re-formatted, data should stay intact. (as far as everything I've ever seen)