Error loading operating system

After a restore a virtual machine failed to start, the screen remained black and the following error was displayed: “Error loading operating system


All standard solutions like “chkdsk /r”, “chkdsk /p”, fixmbr, fixboot,… did not work.

After some deeper research I noticed that there may be a problem with the disk geometry of the virtual disk. I guess that this occured when we aligned a lot of virtual machines some times ago or something happend during the restore.

Fortunately I found a tool that helped to clean up the mess and made the virtual machine bootable.


  • Attach the broken boot disk (vmdk) to another virtual machine
  • download the tool “Testdisk
  • unzip the tool and start testdisk_win.exe on the virtual machine you use for repair

Select “No Log”:

Select the disk you want to repair:

Select “Intel/PC partition”:

Now select “MBR Code – Write TestDisk MBR code to first sector”:


  • confirm “Write a new copy of MBR code to first sector” with y (yes)
  • confirm “Write a new copy of MBR code, confirm” with y (yes)

Select OK after the new copy of MBR code has been written successfully.

Now select “Advanced – Filesystem Utils”:


In the next window select “Boot”:


If there are mismatches or problems you will get a view like this:


to solve this, select “Rebuild BS”

  • when the rebuild was successfull, leave the tool using “quit” till all windows are closed
  • unattach the virtual disk from the virtual machine
  • power on your broken Virtual machine – it should now boot without any problems!


  1. Joan Resina

    Thankyou for the article, it was so useful to me with a Phisical to Virtual HyperV converted . Only one comment…
    After “Rebuild” I had to select Write and the type of Filesystem (07 NTFS) before quit.

  2. Olumide Oyetoke

    Thank you so much for this info.

    This is the PERFECT resolution to an unbootable VMDK after exporting a WinXP virtual machine from VMware to ovf format, and importing to VirtualBox but keep on getting the “Error loading operating system”

    I also followed the last step by Joan Resina “After “Rebuild” I had to select Write and the type of File system”

Leave a Comment

Your email address will not be published. Required fields are marked *