Windows.old automatically deleted the day after installing Windows 10

bro67 · 16 Nov 2018

trashboi98 said:

For future reference, though, how would I have been able to recreate the System Reserved partition in that situation?

A simple websearch would have given you info quicker than complaining about someone suggesting to upgrade to Windows 10 and something causing the Windows.old to be deleted, which I doubt was caused by Microsoft.
Rebuild System Partition

The second way here we can put forward is to rebuild the system partition. If you don't want to pay a penny to do the lost partition recovery, try this method. Note that this requires you have the Windows installation disk. Now follow the instructions to begin.
Preparatory work:
Boot the computer using the Windows installation media for your running OS. Then on the first installation screen, press SHIFT+F10 to bring up the command prompt.
Now run the following commands at the command prompt.
Step 1:
bootrec /fixmbr
Step 2:
diskpart
select disk 0
list partition
select partition n (n is the Windows OS partition)
active
exit (exit diskpart)
Step 3:
bootrec /fixboot
Step 4:
bootrec /rebuildbcd

NavyLCDR · 16 Nov 2018

@bro67's is one way of doing it. You can also use diskpart to shrink the C: drive partition by 150-200MB. Create a new partition in the empty space, format it (I prefer FAT32 because it is more universal), mark it as active (if an MBR drive). Then I prefer the bcdboot command over bootrec. You can run bcdboot /? in a command prompt or powershell window (with admin rights) and see the different options for bcdboot. This method works on both legacy BIOS and UEFI computers. Most UEFI computers need a FAT32 partition to boot from, so you can't use the Windows NTFS partition as the system partition. But you system was more than likely legacy BIOS with an MBR partitioned drive so @bro67's method would likely have worked as well.

Somebody who has the steps memorized can recreate a system partition in about 1 minute + whatever time it takes the resizing of the Windows partition to complete.