Solved Drives do not show up in File Explorer

I just noticed that certain drives were not showing up in File Explorer in my main Windows 11 desktop. The drives were any flash drives and the Blue Ray optical drive. Note external HDD and SSD drives showed up OK. By trial and error I found out that if I changed the drive letters for them they started showing up.

Can anyone explain this? Is there something I can do to fix it so it doesn't happen again?

To summarize what I had to do:

• I changed the flash drive from G: to H:
• I changed the Blue Ray drive from M: to L:

I found that assigning static drive letters in the higher end of the alphabet stopped all the confusion Windows had with my drive letters where the letters would randomly change.
What does the registry say? Is anything listed there that is in conflict that is causing your drive letters to change. HKEY_LOCAL_MACHINE\SYSTEM\MOUNTEDDEVICES
.

This is what I am seeing for Mounted Devices before and after the drive letter changes. The only strange thing I see is J: which I don't know what it is for.

BTW, I did replace the two SSDs (C: and D:) recently with two new ones. I cloned the old ones to the new ones.

This link may be useful:

I just discovered why G: is unavailable. However, I haven't figured out what is prevented M: from being used for the optical drive.

Note I found the following with the flash drive assigned to H: and the optical drive assigned to L:.

1. If I open File Explorer and entered G: in the navigation windows the contents of G: are shown. Note G: is not shown in File Explorer otherwise. I finally realized that these are the backups for my Samsung S21 phone.



2. If I look at my desktop I found a shortcut to G:. This threw me for a moment because it is named My Book. I used to have a WD My Book (6TB) external HDD connected to my computer a couple years ago but not any more. I now realize that back then the drive must have had the drive letter G:. This appears to be only a coincidence.



3. If I bring up the Acronis True Image backup program I see that the backup entry for my Samsung S21 phone. What is strange that the destination for the backup is: E:\Acronis Backups\DarkMatter\PHONE. Note E: is a WD EasyStore (20TB) external HDD.



4. If I browse to the backup location for the phone on the EasyStore external HDD I see this file:



5. If I click on Browse files then the drive G: is opened showing the mobile backup data.



6. If I browse my user AppData I can find a reference to the data there. Acronis True Image must have assigned the drive letter G: to this path.

I also posted the same problem in the Acronis user forum. I got no replay there. To my surprise someone from Acronis tech support saw this post and called me yesterday. He did a remote connection to my desktop computer. He was able to use a workaround that changed the drive letter that True Image used from G: to a letter of my choice T:.. I can use G: with my flash drive again. However, he had no idea why the drive letter M: had the same problem or whether it was even caused by True Image. I will leave this thread open a while longer in case anyone has any other ideas.

Update:

Note during this whole time both G: and M: were available for use according to Disk Management. If a program is going to use a drive letter shouldn't it communicate with Windows so that drive letter is made unavailable for any other user?

To my surprise M: is working with my optical drive again. Did the Acronis support tech fixing the problem with G: mysteriously fix this also? I guess I will never know. In any case It is probably best to leave things alone as long as everything is working OK again.