Hi Rick,

here goes how I ended up solving it:

1. I manually removed the previous version (installed with a setup.exe - which is just a launcher for the MSI file).

2. I install the new MSI version using the /i switch.

From that point on, I can install new versions using the switch /faum (which means, "replace all files" and "rewrite all registry entries")...

I think that should work well...

I appreciate your help!