1. AndyCalling's Avatar
    So, I moved to the Release Preview once it was clear the April release was delayed. Weirdly, once updated to the preview an 'OEM' partition appears in File Explorer with a drive letter. This is the ~450MB partition that used to be called the recovery partition at the beginning of the boot drive (I have no special OEM partition, this was a clean install of W10 on my own build, there is no OEM). Clearly it should not have a drive letter, and I've had to edit the registry to stop the constant warnings about a drive being full because of this. So, turns out if I restore my image from before the update the 'new' drive letter goes away. Then I switch to Insider Release Preview again and back comes the unwanted drive allocation for this partition. Nothing I do with Diskpart or the drive manager gets rid of the letter (might do temporarily but it gets reallocated on a reboot). Am I to assume a) this happens to everyone on Insider these days, and it will go away once I've returned to the stable build on full role out day b) this is a bug with this build of Windows and even if it remains when I return to stable, everyone is seeing this and MS need to deal or c) this is just something wrong with my PC, probably needing a reinstall of everything from scratch because, you know, Windows. Do let me know folks, because I can find very little information on this issue and I want to understand what's happening before the full role out of the April update.
    04-23-2018 11:04 AM
  2. orlbuckeye's Avatar
    An OEM partition is created in the factory by the OEM. If you do the upgrade this partition isn't touched. It contains the OS that was originally installed by the OEM.
    04-26-2018 12:27 PM
  3. AndyCalling's Avatar
    Not this one. I am the OEM, I built the system. This is the 450MB standard Windows 10 'recovery' partition which Disk Management now refers to in Status as 'Healthy (OEM Partition)'. It should be hidden, and it used to be marked as the recovery partition, but not any more. Now it has a drive letter and everything. It remains impossible to affect with Disk Manager and any changes made through DiskPart won't persist past a reboot. I can restore my pre-insider image and the problem goes away, but if I then switch to insider again and update this same partition pops up with a drive letter again. Seems to be something that is supposed to happen when on an insider build? If so, it should disappear when the release version of the April update comes out. If not, then this issue might persist. So, I'm trying to find out from here so I can act accordingly when the final update comes out.
    04-26-2018 01:54 PM
  4. AndyCalling's Avatar
    Well, it appears that the insider programme is so unpopular that no-one else is able co confirm this issue/feature, presumably because they are choosing to avoid it. I shall widen the net then.

    If you know anyone who has ever tried insider on W10 even once (though the more recently the better, as things may have changed) can you check with them and ask if this issue is normal or not? I'm really hoping to find out before the 30th so I know how best to handle the final update when it arrives.
    04-27-2018 12:32 PM
  5. AndyCalling's Avatar
    I have found a number of others with the same issue now, but I still can't get confirmation that this is a universal issue (or otherwise). I shall experiment with the release build tonight. It would have been a bit easier to work out the best approach if I'd had some feedback, but I shall proceed without and see how it goes, then I'll report back to help others.
    04-30-2018 12:12 PM
  6. AndyCalling's Avatar
    OK, so even returning to my old pre-insider image (recovery drive loses the letter and returns to being seen as a recovery drive in disk manager) and updating to the release version, this issue comes back. So it's in the release version too. The recovery partition is seen by disk manager as an OEM partition and it gets a letter. Problem is, it is a recovery partition (correctly marked when I investigate) it's just that disk manager can't see it. You can remove the letter with Diskpart but it returns at reboot.

    I have a solution. I don't usually resort to this kind of thing, but download the free edition of Minitool Partition Wizard from here:
    https://www.partitionwizard.com/free...n-manager.html
    but don't tick to OK box to install the 'bonus' search bar by mistake. It is a legit tool, just that one thing to avoid. You can remove the drive letter with the tool by choosing to change the drive letter and selecting 'None' and it will stay gone. This utility will also confirm to you that the partition is still marked as a recovery partition, so don't muck it about. Just remove the drive letter then hit Apply. You can then close and uninstall the tool which cleans itself away properly it seems. Problem gone.
    04-30-2018 05:28 PM
  7. ja206's Avatar
    I updated to april update today and a new 500 MB partition shows up and is saying it is full with no files in it
    04-30-2018 07:55 PM
  8. Devhux's Avatar
    Same here on my new XPS 13 9370 after updating to the April Update.
    04-30-2018 10:41 PM
  9. AndyCalling's Avatar
    It isn't a new partition, it was the recovery partition and was always there, in Disk Management, but it didn't have a drive letter. Follow my solution above.
    05-01-2018 04:18 AM
  10. ja206's Avatar
    Ok thank you!
    05-01-2018 02:27 PM
  11. ja206's Avatar
    Question... This post suggests just removing the drive letter. Would that work? https://www.google.com/amp/s/www.how...n-windows/amp/
    05-01-2018 02:32 PM
  12. AndyCalling's Avatar
    No. Disk Management will only offer the option 'Help' on the right click menu for this partition, and whilst Diskpart will seem to work, the letter will return upon reboot. Use the method I have specified.
    05-02-2018 04:33 AM
  13. alistairgd's Avatar
    OK, so even returning to my old pre-insider image (recovery drive loses the letter and returns to being seen as a recovery drive in disk manager) and updating to the release version, this issue comes back. So it's in the release version too. The recovery partition is seen by disk manager as an OEM partition and it gets a letter. Problem is, it is a recovery partition (correctly marked when I investigate) it's just that disk manager can't see it. You can remove the letter with Diskpart but it returns at reboot.

    I have a solution. I don't usually resort to this kind of thing, but download the free edition of Minitool Partition Wizard from here:
    https://www.partitionwizard.com/free...n-manager.html
    but don't tick to OK box to install the 'bonus' search bar by mistake. It is a legit tool, just that one thing to avoid. You can remove the drive letter with the tool by choosing to change the drive letter and selecting 'None' and it will stay gone. This utility will also confirm to you that the partition is still marked as a recovery partition, so don't muck it about. Just remove the drive letter then hit Apply. You can then close and uninstall the tool which cleans itself away properly it seems. Problem gone.
    I have the same crazy issue since my PC applied to April update today, very annoying - not sure how this could have passed testing.

    I also loath to have to install a tool and tinker switch settings just to stop the annoying popup each boot, but I'll give it a go and hopefully MS patch this out soon.

    Thanks for posting the tip.
    05-18-2018 11:21 AM
  14. 4voeter's Avatar
    I was not in favor of downloading some program for it.
    However the list of this command did the trick as well.

    Windows (key)+ R(un)
    cmd
    diskpart
    list disk
    select disk 0
    detail disk
    select volume 1
    remove letter=I ( well it was I in my case)
    05-20-2018 08:54 AM
  15. AndyCalling's Avatar
    Tried diskpart to remove the drive letter like above but it returned every time after a reboot. Worth a go, but if it doesn't stick try my method.
    Yesterday 08:32 PM

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