Disk Management Blocking Use Of Mode "H"

I'm trying to change the defaulted letter "I" and assign "H" to an external disk drive. But Disk Management is not showing "H" as available (see attachment Mode Letter Problem - 1). That is probably because in Computer -> Devices it is showing "H" as being assigned to a "Removable Disk" (see attachment Mode Letter Problem - 2). But I did not put a disk in there at "H" and then detach it. And the left frame in Explorer showing all of the disks does not show "H" assigned. It's possible that many months ago something may have been defaulted and briefly assigned "H" but if so that was a very long time ago.
How do I fix this?

Download USBDeView. Then watch my video. View any installed/connected USB device on your system

(Chose 1080p and full screen).

Thank you F22 Simpilot. I installed USBView but it does not help. It shows four (4) drive letters all on one device (see attached). And I don't even know what that device is. I use "F" for USB disk for backups (disconnected now); "G" is for a USB disk on a different computer (on the LAN); "E" is the same story as "H" - it may have been automatically default assigned once but that was a long time ago.

Any ideas?

NewW7User said:

... I installed USBView but it does not help. It shows four (4) drive letters all on one device (see attached). And I don't even know what that device is. Any ideas?

This is usually an SD card reader that can support up to 4 cards, but without any cards inserted at present.

Bree,
I didn't get this computer new and don't have a card reader attached to it (unless it's hidden under the covers).

SIW2,
I came across some warnings on a website about HKLM Mounted Devices entries being cross-linked to other keys and therefore deleting is a big risk in just deleting them. Is that not correct? Oddly (or interestingly) - the data entries in Mounted Devices for the four letters that I noted above are identical.

You could always A) create a system restore point and B) right click that registry key and export. I'd do both. Besides, you should have periodic disk clones anyway.