Most likely the error message “We couldn’t update the system reserved partition” is unique to Windows 7 (or Windows 7 systems that were upgraded to Windows 8 / 8.1) based computers when attempting to upgrade to Windows 10. You may also get the following error code: 0x800F0922
The 100MB System partition has only about 50% free space remaining and needs to be resized to 350MB which is the standard size for Windows 8, 8.1 and clean installs of Windows 10.
You will need a third party utility such a Partition Master (there is a free version) that allows you to shrink the front of the Windows 7 / 8.1 partition in order to extend / increase the size of the System partition to about 350MB.
Note: Based on user reports, I'm now recommending that you increase the size of the System partition to 400MB as the new minimum and 450MB as the optimal size. Please make the appropriate adjustments in the instruction listed below.
Start by downloading and installing either EaseUS Partition Master free:
MiniTool Partition Wizard free: http://www.partitionwizard.com/free-partition-manager.html
Partition Master has an easier to use interface in my opinion so I’ll use it for this article.
1) Run Windows 7’s Disk Management utility to check the current size of the System partition. You should see a 100MB System Reserved partition. If you right click on this partition and select ‘Properties’ you will see how much free space is remaining.
Note that you may also have in addition to the Windows 7 partition a “Recovery” partition and possible a “Tools” and or “Utility” partition. These partitions should remain untouched.
Next you need to increase the size of the System partition from 100MB to about
2) Run Partition Master and you should see a 100MB System partition and the C: Windows partition. Note: The disk drive I’m using is 1TB in size with a retail version of Windows 7 installed.
3) Right click on the C: Windows partition and select the ‘Resize/Move partition’ option from the dropdown list. In the upper left corner (Decide size and position) move your mouse cursor over the left edge of the partition until you see the Left/Right pointers. Now left click and drag the edge of the partition to the right ever so slightly. The value in MB will most likely be way too large so go to step #4.
4) Now change the ‘Unallocated Space Before’ value from whatever is displayed, 12839.2 MB in my example:
260 MB 340MB to get closer to a true 350MB 450MB partition size) and click ‘OK’.
Note: If you see some unallocated space suddenly displayed after the C: Windows partition, as shown below.
Move the cursor to the right end of the Windows partition and when you see the double arrow hold the left mouse button down and drag the end of the partition all the way to the right until the partition is at its max size and click ‘OK’. Your display should now look as follows:
5) Right click on the System Reserved partition and select the ‘Resize/Move partition’ option from the dropdown list, change the Partition Size value from 100.0 MB to
350.0 MB 450.0 MB (or the max value allowed based or the unallocated space you created) and then click the ‘OK’ button.
6) You should now see the partition sizes that will take effect after you ‘Apply” the changes.
7) Click on the ‘Apply’ tab in the upper to make / apply the changes to your disk drive. When prompted click on the ‘Yes’ button. A reboot will be required to complete this task so click ‘Yes’ when prompted.
It will take about 30 seconds before your computer reboots. Partition Master will then display a DOS based graphical display of the progress.
8) After Windows 7 has finished loading open Disk Management and you now see the new size of your System partition.
You should now be able to upgrade to Windows 10