As usual, Lifehacker has a good read about the subject in question.
One of the most persistent myths about Windows is that you need to reinstall the operating system regularly to keep it running at top performance. Let’s take a look at the real problem and how to fix it.
Today we’re talking about the myth that Windows slows down over time, and how to solve the problem. The reality is that Windows doesn’t slow down if you just take care of your PC a little more. Follow these procedures, and you won’t have to wonder if spending hours backing up data, installing from disc, and re-installing your essential applications is really necessary.