Here is the scenario: an HP all-in-one PC gets a virus and as a precaution the owner wishes to reinstall Windows.

The recovery drive on the PC is intact, but attempting to use the Windows 8.1 troubleshooting tools to “Reset your PC” (in effect reinstalling Windows) raises the error “A required drive partition is missing”.

This seems to be a common scenario in cases where the PC was supplied with Windows 8 and upgraded to Windows 8.1. The problem seems to be that Windows 8.1 makes some changes to the drive partitions that make it incompatible with the Windows 8.0 recovery partition.

Here is the workaround I used:

1. In Windows 8.1, make a recovery drive. To do this, first connect a USB drive that you are happy to have wiped. It will need a capacity of around 16GB or more. Then run Control Panel, search for “recovery”, and choose Create a recovery drive.

2. When creating the recovery drive, make sure the option to include the recovery partition is checked. This will copy the recovery partition from the PC to the USB drive.

3. When you are done, you will be able to boot from the USB drive. You could choose the Reset option from there, however you will still get the error. First, go to Troubleshooting and Advanced and select the command prompt. When the command prompt opens, type:

diskpart

Now type:

list disk

You will see two disks (or more) listed, one for the USB boot device, and the others the disk(s) in the PC. Select the internal boot drive. It is normally obvious from the sizes which is which. Select it by typing:

select disk n

where n is the number of the drive as shown by list disk.

WARNING: the next step will delete all data on the selected drive. If in doubt, back out and make a backup of the drive before proceeding. If something goes wrong, your PC will no longer be bootable and you will need recovery media from the manufacturer, or to buy a new copy of Windows.

Once you are happy that it is safe to delete everything from the drive, type:

clean

or

clean all

The first command does a quick removal of the partition table from the drive but does not zero the data; it will be invisible but possibly recoverable using data recovery tools. The second command zeroes all the data and takes much longer (several hours), but it is more secure, if for example you want to sell or transfer the PC.

Once this is done,reboot the PC using the USB recovery drive. Select troubleshooting, then Reset your PC. This time it will work and you will be back in Windows 8.0.

Note: This scenario is common enough that it seems to be a flaw in the Windows 8.x recovery tools. I do not understand why Microsoft has so little regard for its users attempting to recover Windows (and usually highly stressed) that it has not fixed this problem.

Note 2: What if you cannot boot into Windows 8.1 to make the recovery drive? I have not tried it, but in theory it should be possible to create a recovery drive on another PC and copy the recovery drive to it.