Personally, I do a clean re-install of windows at least once or twice a year. The important thing to do is to back up all your personal documents, photo's, anything that you wouldn't want to lose. Then back up any programs/games that you don't want to have to re-download all over again.
On newer versions of Windows, it's a lot easier to perform a Windows re-install than it was on previous versions. It generally solves a lot of issues and might be an option for you.