Innstall for SL360 fails

I'm trying to reinstall SL360, but I get this message every time. I'vre rebooted 4 times...

error message

I have admin rights, I have installed as admin and I just reinstalled SL2 to test this (and to get some work done).
How can I fix this?
The reason for reinstalling SL360 was to see if it would stop minimising the ribbon all the time... Has anyone else had that problem?

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