I have recently tried to update to the Windows 10 Creators Update on a few of my computers. Two of them kept failing, stating “we couldn’t update the system reserved partition”:

I obviously wanted to get the latest & greatest build of Windows 10 and so went out to find how I could resolve this.

They were both HP Business machines but were built using separate media and there’s not much else they had in common, so I was struggling to see what the problem could be. After a few hours of troubleshooting, I realised that I had recently updated the BIOS on both of these machines. So it appeared to be something to do with that.

I then had a look in the System Reserved (SR) partition referenced in the error (this is the partition that is used by Windows to store the boot executable files) and found various BIOS files in there.

I learned that, when the BIOS is updated on a HP business machine, the updater takes a backup copy and places them into the SR partition. It also puts the new BIOS in there. These take up space in the SR partition, causing the Windows 10 update to fail

Once I had discovered this, a solution was easy to create :-)

Please note: this can be quite a complex process so please ensure you are familiar with the command prompt, as well as the diskpart command. before you follow the below. This worked in my environment but I cannot guarantee this will fix your issue, and running the below commands incorrectly could render your machine unusable.

1. Open command prompt as an administrator
2. Type in diskpart and press enter
3. Type in list disk and press enter
4. Identify which disk is your main operating system disk – this would typically be Disk 0 but it’s not always the case
5. Type in sel disk x, with ‘x’ being the OS disk number, and press enter
6. Type in list part and press enter
7. Identify which partition is the partition labelled “System” – this is 99MB in size. In my case it’s Partition 2.
   
8. Type in sel part x, with ‘x’ being the System partition number, and press enter
9. Type in assign letter=x, and press enter (if you already use the letter ‘X’ for something else, please use an alternative letter)
10. Minimise this window for now (you’ll need it later)

At this point, your System Reserved partition will be accessible via the ‘X’ drive (or whatever you decided to use) on your computer. The offending folder is called HP (this is in the EFI root folder). Now a drive letter is attached, you can manually move the HP folder to a different location. If you’d prefer to just delete the folder, you can do this via the Command Prompt too:

1. Open a new command prompt as an administrator
2. Type in rd X:\efi\hp /S /Q and press enter. If you used a different letter in step 9, use this here.
3. Close this the second command window

Finally, you’ll need to remove the drive mapping:

1. Go back to the original command prompt
2. Type in remove letter=x and press enter.  If you used a different letter in step 9, use this here.
3. Close the command prompt

Then, attempt the Windows update again. It should now complete successfully!