“Undefined external error” when trying to access my midi device on a Windows system.

Midi Ox is a free and easy tool to analyze incoming/outgoing midi data with your midi device.
Download MIDI-OX here

For one user, we received “Undefined external error” when trying to enable his midi device’s inputs or outputs.

The solution:
“Hold down function/Windows key and press the letter R. This will open the Run window.

Type in: regedit to open the Registry Editor

Press CTRL + F on the keyboard to open the search window. Copy and paste the following key in the Find what field.

4D36E96C-E325-11CE-BFC1-08002BE10318
(make sure there are no leading or trailing spaces)

There will be several registry keys that look very similar. You can confirm that the search function has located the correct key because the (Default) value is Sound, video and game controllers and the Class is MEDIA

Right-click in the right hand pane and choose New -> Multi-String Value
Under the Name column right-click New Value and select Rename and type UpperFilters (case-sensitive)

Double-click UpperFilters and under Value data: type ksthunk (case-sensitive)

Click File Exit to close the Registry Editor.”

Knowledge Base