Once in a while, you might want to reinstall Windows, especially if your system starts to get bogged down, or if you’d had a catastrophic loss from a virus attack. The problem is that reinstalling Windows will delete personal files and data, so what do you do? Check out this article over at InformationWeek which offers a step by step on the process complete with videos of each step.
You could always do constant backups of your system (NOTE: if you have never performed a backup, start now!), and even if you are, this article is a fairly valuable resource in order to keep your data safe and secure.