A reformat or three will not harm th drive. I tend to reformat if a). there is a factory restore disk as this makes it a doddle and can save a lot of time mucking around or b). there are many, many problems that are compounded. There is little point in reformatting for simple problems as they can usually be sorted PDQ. The weekly use of Ccleaner, click here and regseeeker, click here will keep your system in top shape.