Mouse not working, Device Manager shows PS/2 Compatible Mouse exclamation mark

I had this problem after a Win 10 update. The mouse stopped working both USB and Bluetooth. I tested a different mouse and that didn't work either. Touchpad worked fine. So I called Dell tech support and they suggested I uninstall Windows update and re-install the chipset drivers that they provided. I did both and mouse still didn't work. Then tech support suggested I do a Windows Restore. Again that did not solve the problem. Then they suggested I do a Windows reinstall. At this point I got annoyed since I have 30 programs that I use for my business and a total Win re-install is out of to question. I thought there must be another simpler way to solve this problem. So I did an online search and found a fix. It was a very simple problem and needed a very simple fix:

I was able to fix this problem by adding a missing MultiString value to this registry key:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Class\{4D36E96F-E325-11CE-BFC1-08002BE10318}

Value Type: Multi String

Value Name: UpperFilters

Value: mouclass

An article that explains it in a very round-about way is here:

https://answers.microsoft.com/en-us/windows/forum/windows8_1-hardware/keyboard-and-mouse-get-device-manager-code-10/326f7c0d-14cb-45c2-a705-32d3a2ab07d6

The Multi String Value Name: UpperFilters was missing so I added it and the mouse started working and everything is good to go!

I was very disappointed with the Dell support team I contacted. They gave me the run around for 3 days for such a simple problem.