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[ The PC Guide | Troubleshooting and Repair Guide | The Troubleshooting Expert | Troubleshooting Specific Components | Troubleshooting Hard Disk Drives | File System Problems ]

The hard disk's file structures have become corrupted or the data on it is unreadable (an existing disk volume is acting as if it is unformatted, or there are very serious disk errors)

Explanation: The hard disk is generating error messages or is otherwise behaving as if it has become seriously corrupted. An existing, working hard disk may be acting as if it had been wiped clean, or had been never formatted. Strange error messages or very large quantities of files may be corrupted or wiped out. Note that small numbers of lost clusters or other minor file system corruption are often a result of more benign situations and are discussed here instead. (Bear in mind that if you don't scan for file systems regularly, they can accumulate and make the situation look a lot more dire than it really would be if the disk had been maintained properly.)

Diagnosis: There are a myriad of possible causes for a hard disk that is experiencing a large amount of corruption; most of them are, unfortunately, pretty serious. In many cases it is not the hard disk itself but rather an external factor that is causing the problem.


  • Make sure you thoroughly scan the system for viruses, using an up-to-date virus scanner. Many viruses take hard action against the file system. It is a relatively simple thing for a virus to change the disk's major structures so that it appears empty or invalid.
  • Make sure that you are using the correct type of disk utilities. Using a disk utility not designed for Windows 95 on a Windows 95 system, or using one not aware of FAT32 on a FAT32 volume, can cause large amounts of corruption on a disk that is otherwise functioning properly.
  • If you have just installed the disk or made changes to the inside of the system, try this troubleshooting section that focuses on common installation problems.
  • If you have just moved a hard disk from an existing system where it used to work, the problem may be related to a change in how the BIOS references the disk. See here for more on this issue.
  • Check for resource conflicts. These can cause problems with the hard disk.
  • Check to make sure the hard disk has been set up correctly in the BIOS.
  • Try disabling the enhanced performance settings in the system BIOS, and dropping down to a lower PIO mode as well. Some of the settings that don't always work in all machines include Block Mode and 32-bit access.
  • Make sure that the IDE cable is not too long. Try swapping the cable or using a shorter one.
  • You may have a real problem with the disk that is causing the difficulty. In my experience it isn't too typical to find repeated file system problems without a real disk problem manifesting itself in other ways but it is possible. Troubleshoot the disk here.

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