[Znod]

Welcome. Is your problem a new one? Did you install any new software shortly before the problem began?

If your answers are yes and no, respectively, I'd (1) scan like crazy for a virus or malware. Then, I'd (2) run a memory test. If you have found nothing wrong at this point, then I'd (3) do a repair install of Vista. If your second answer is yes, then I'd uninstall the new software and do a system restore presumably to a point before the software install prior to doing (3). If no luck at this point, then I'd format and reinstall.

If your problem was present from the outset with your computer, then I'd contact your manufacturer's telephone support. If you problem always has been present, then surely you still are in warranty.