Thanks, that worked nicely!
Now I get another error when trying to open a .pgn-file:
File -> Open results in the error above, but I can open the file if I use Edit -> Paste PGN.
The file was created in Tarrasch, but I get the same error if I try to open games from websites etc. The file is not read-only.
No answer comes immediately to mind on that one. I can't duplicate the problem on my end. I'll have to mull this over, but right now I have nothing.
I'd almost be willing to bet I know the problem.
Uninstall the previous install, if you can.
Then create a new folder on C:\, something like "Program Files (64-bit custom folder)". Install the program into that folder, and it should work.