Rebuilding the Windows System Reserved Partition

Last updated on July 7, 2017

I’ve been googling this like crazy for the past couple of days to find out how rebuild a Windows 7 System Reserved partition. So lets start with the back story of why I needed to do this.

A few weeks ago I upgraded my Samsung 840 EVO to a new 850 EVO, and installed the 840 EVO in another computer here. In both cases I used Samsung’s Migration Tool to copy the old drives to the new drives. In both cases, at least so far as I can tell, Samsung’s tool renamed the 100MB System Reserved partition to “Data” and filled it until it had 5MB free. For whatever reason, the file filling the partition is completely invisible.

The problem with this problem, is that while the system works just fine, if you use Window’s image backup utilities (wbadmin), for a drive that’s smaller than 500MB, there must be at least 50MB free. Well in the default configuration from a Windows install, there’s about 70MB free and everything backs up just fine. However, with only 5 MB free, the volume shadow copy can’t be made, and the backup will error out. Backups failing was the symptom that clued me in that the system reserved partition was messed up again.

In any event, I’ve tried a couple of ways to recover this situation without resorting to the most oft given advice of format and reinstall—advice I find simply appalling in almost every situation that it’s given. The first time I had this problem, I just repartitioned the disk so that I had more space on the system reserved partition so it would back up—it also helped that I needed >300MB since I was going to try and convert the computer to boot off UEFI instead of the legacy BIOS.

Readjusting the partitions does have side effects, namely it can potentially result in corrupted data if the tool moving the files around to make room doesn’t do the job properly. I’ve never been thrilled with this potential issue, and I’ve had it crop up in the past.

A safer approach, at least in my eyes, is to simply rebuild the system reserved partition from scratch. Oddly MSFT doesn’t seem to include a mechanism to do this in a running system, at least not that I’ve been able to find. However, it can be done from a Windows recovery disk.

Warning: This is what I’ve found to work, if you’re not comfortable with these steps you should find someone else to help you. Fixing computers, and more precisely fixing your computer, is not my job; I’m offering this information solely because I could not find any instructions online that covered it.

FOLLOWING THESE STEPS CAN RENDER YOUR COMPUTER UNBOOTABLE.

FOLLOWING THESE STEPS IMPROPERLY CAN RESULT IN THE LOSS OF DATA.

PERFORM A FULL BACKUP BEFORE DOING ANYTHING DESCRIBED HERE.

Also, I’ve only attempted this on a single boot Windows 7 machine, if you have multiple OSes this probably won’t work right. Also if you’re using Windows 8 or 8.1, the procedure should be the same, but I can’t make any guarantees of that.

As a side note, it’s been pointed out to me that the recovery system may not mount the system reserved partition as drive ‘c:‘ as I note in step 6. If that’s the case for you,  you’ll want to replace c: with the drive letter that your system reserved partition mounted as. If it didn’t mount automatically in the recovery environment, you’ll need to mount it before you proceed beyond step 6.

What you need:

• A bootable Windows Recovery CD

How you do this:

1. Boot the computer off the recovery CD
2. If it prompts you to fix a problem with the boot files, click no
3. Select your current Windows Install and select the top radio button “Use recovery tools that can help you fix problems starting Windows.”
4. Click Next and the second menu of options will be displayed
5. Click command prompt form the second menu
6. Verify that the recovery environment has mounted the system reserved partition as c:
   1. change to the “C” drive by typing “c:” at the command prompt
   2. type “dir /a" at the prompt
   3. verify that this the system reserved partition by noting the existence of the files “bootmgr” and “Bootsec.bak”, and the folders “Boot” and “System Volume Information”. There may also be a $Recycle.bin. In any event, you should NOT see a Windows, Program Files, or Users directories.
7. If you’ve properly verified that the C: is the system reserved partition, you can start with the rebuild process
8. Format the system reserved partition
   1. Change drives to X: or D: by typing "d:" or "x:"—the drive doesn’t matter you just don’t want to be on C:.
   2. type “format c:“
   3. You’ll be prompted to type the volume label which you’ll find at the top of the dir output we previously did (it’ll probably be Data if Samsung Migration messed it up like I did mine)
   4. You’ll be further prompted if you’re sure you want to do this, this is your last chance to back out if you’re not comfortable; otherwise type yes.
   5. You’ll see a report that the disk was formatted, it should say there’s about 100MB on the volume.
9. After formatting the volume, you’ll need to recreate the boot files.
   1. Close the command prompt and choose “Startup Repair” from the menu.
   2. It will do it’s thing and prompt you to reboot when finished
   3. Click “finish” and let the computer reboot
10. When the compute reboots you’ll need to boot into the recovery CD again, (if you miss this, you should get an error that boot file is missing)
11. When the recovery CD starts, it should notify you that there is a problem with the computer’s startup and it can attempt to fix it (same dialog that may have come up in step 2). Click “repair and restart” here.
12. Your computer should boot into Windows normally

If your computer doesn’t boot into windows after the second repair run, you may have to do a 3rd. I’ve found a number of people posting that you often need 3 runs of the startup repair to fully fix a non-booting computer. I’m not sure why, but it’s something to try. If that doesn’t work, then you’ll need to restore from backup or perform a reinstall.