In Windows Explorer Right Click your C: Drive, select Properties, Tools, Check Now, Scan for and...bad sectors. (This will run chkdsk /f). It will probably say the drive is in use so choose SCHEDULE DISK CHECK. This could take an hour or so depending on the size of the drive. So if thee isn't a problem with the drive then you might have some sort of virus infection. Do you have antivirus running? Is it free or paid? If that isn't it I would suggest backing up all your data and erase/reinstall windows. Let me know where you stand....