You can always borrow a clean copy of the Windows 7 version which comes on your machine to do your clean install. This is what I do to overcome the corruption that always occurs when trying to uninstall bloatware like Norton or Office trial.
As long as it's the same version licensed to that machine, it should auto-activate after install or only require a quick robo call to MS which exchanges numbers.
But remember, such a clean install will need a word processor since Works isn't in Windows 7, the adobes (flash, reader), java runtime (they have a free word processor), and whatever else you like that's included by your manufacturer.
Fortunately, Windows 7 has most all of the
drivers in its installer and via Windows Updates.