RH6 uninstall doesn't work

I moved my Rhino 6 license to anther computer. Now Rhino is asking me to uninstall the program from the old computer. Loocking for uninstall I found rhino being installed three times. For the eldest version uninstall worked after I disabled all kinds of firewalls and virus scanners.
But there are still two installations remaining which I cannot uninstall. They are named 6.12.19029.6381 and 6.13.19058.6381
They seem to start to uninstall but then nothing happens.
Any idea how to solve this?
And by the way why was it installed three times?