It could just be a bad sector, that happens quite often. Scandisk usually closes it off for you and just moves the data around. The reason I suggested safe mode is that sometimes other applications can conflict with scandisk (especially things like norton and mcafee). Safe mode removes all those from the equation. When you start to have hard drive problems, it is a good idea to run the diagnostic from the drive maker (it is just one floppy that you boot to). It tests out the drive and will tell you if there are any problems mechanically.