From what I've learned and experienced, it's generally a good idea to scandisk and defrag once a month, and reformat about once a year. Thats what I do, keeps things running smoothly. Or atleast If I were you I'd buy a USB Pen drive or in some other way back up your data first. Or you could just wait until something messes up. My old celeron 400 went for three years of toil and abuse without being reformatted before it left my possession.