Accidentally deleted 16mb MI reserved partition

Copper Contributor
I accidentally deleted 16 MB Microsoft reserved partition. PC didn't Boot after then. It was stuck without booting saying "unable to mount boot volume". I somehow managed to fix it by rebuildbcd. And now, it's booting fine. Now that 16mb partition is "unallocated". Do I need to do Anything? What was that 16mb partition? It wasn't the EFI partition. My efi partition is 256mb.
Thanks!
6 Replies
Hello,

it's Microsoft reserved partition (MSR)
Beginning in Windows 10, the size of the MSR is 16 MB.
The default partition layout for UEFI-based PCs is: a system partition, an MSR, a Windows partition, and a recovery tools partition.

source: https://docs.microsoft.com/en-us/windows-hardware/manufacture/desktop/configure-uefigpt-based-hard-d...
So, should I worry that I don't have it now? It's showing unallocated!
If it's working then don't bother but next time make make sure you clean install Windows fomr a USB and on the installation screen delete all the partitions belonging to Windows and let them be created again.
I've a backup of my gpt partition table. Will it help to recover that deleted partition? If not, why?
I'm not sure.

Hi @ben888 

 

Likely, will not be a problem at all. It's a remnant of the old days but perhaps in some rare instance some system out there will need it for who knows what, maybe some legacy application or something we've all not heard of. I remember this partition going back to the days of XP and not knowing what the heck it is. 

Also, Microsoft also expecs it. Per Wikipedia Microsoft Reserved Partition:

The MSR should be located after the EFI System Partition (ESP) and any OEM service partitions, but it must be located before any primary partitions of bootable Windows operating systems. Microsoft expects an MSR to be present on every GPT disk, and recommends it to be created as the disk is initially partitioned.

I think that's kind of a CYA response by someone working for Microsoft but it's 16 MB, throw it in there and forget about it until some exploit comes along where we need to delete it!

 

-Jason