[quote]Hmm, how Opera was installed: For all users, for one user or standalone mode? Is Opera running with admin rights? Is Opera's profile folder acessible?[/quote]

There is only one user on this computer. That is (of course) an administrator. How do I check whether Opera has Admin rights? Yes, Opera's profile folder is accessible.

At least you have some settings.

All I get - every time I open OPERA 25.0 is a message that "Your preferences files cannot be read. Some features may be unavailable and changes to settings won't be saved."