If you managed to go into Disk Management in Windows XP and somehow click “Mark Partition as Active” accidentally, this could render your computer unbootable. If you are so lucky that you haven’t rebooted yet, here is one possible solution to the problem: mark the partition as inactive using the DISKPART tool:

  1.  Open up a command prompt and type DISKPART.
  2. Type LIST DISK
  3. Type SELECT DISK n (where n is the number of the old Win98 drive)
  5. Type SELECT PARTITION n (where n is the number of the active partition you wish to make inactive)
  6. Type INACTIVE
  7. Type EXIT to exit DISKPART
  8. Type EXIT again to exit the command prompt
  9. Reboot

Mark Partition as Inactive using the Microsoft DISKPART tool

If you have problems booting your computer or the above approach didn’t work for you, you could also try what Microsoft suggests on their help page entitled The computer does not start after you change the active partition by using the Disk Management tool – external link, opens in new window. For your convenience, the content of that page is reproduced below:

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