Got this strange error today with an Excel add-in I'm working on:
The customization cannot be installed because another version is currently installed and cannot be upgraded from this location. To install this version of the customization, first use Add or Remove Programs to uninstall this program
Now this seems pretty straightforward, right? However, the add-in doesn't show up in the Add/Remove programs menu!
No amount of clean solution or rebuild would resolve this issue.
Google didn't turn up any results on MSDN. So I fired up ProcMon.exe to try to isolate the source of the issue and what it was trying to load.
Turns out that it was trying to read values from a key at:
Deleting this key fixed the issue 😀
Still not sure what caused the issue in the first place, but this is a quick any dirty way to resolve it (for now).