11 April 2001

When I start my computer it tells me there may be bad blocks on the hard drive then runs Scandisk.

Your computer is warning you there may be a serious problem with the hard drive. A bad block or sector has been marked by the operating system that it might be damaged and must not to be used in future. You better have a backup if there was important data in that bad block.

When your computer reports a bad block it is essential to run a disk repair program immediately, the Scandisk function included with Windows and Disk First Aid on a Mac are two such programs. Start the computer with your Windows start up disk and type scandisk /a, allow it to repair any problems, agree to it running a surface test and have a pile of blank floppy disks for saving any information. A full scan on a drive with bad blocks can take some hours.

If you have a drive that is showing a few bad blocks you should make sure you are backing up your data regularly. If you have more than five bad blocks or there are more each time the drive is checked you must replace the drive as soon as possible. Bad blocks can be false alarms or a virus acting mischievously but usually it means the hard drive is dying.

Hard drive failure is common so it is worth scanning the drive for errors every few weeks. You can schedule it using the task scheduler on later versions of Windows or run it manually from the accessories folder. Remember that any data on a bad sector will probably be lost: Another reason to backup your data.