Thanks a lot for yr quick reply. To be honest with you, I found this message too, but the forum forgets to say this lusmngr cannot be opened through Vista Home Premium: you need a higher version.
Some other forum says you simply have to make a new account as admin, but that ons doesn't work either. Some other stipulate it had to with MSN, but that does not seem to be installed on my PC. We use life.
One suggestion would probably work: reinstall Windows from scrap on... Not my piece of cake!

In other words, I am still puzzled and looking for a solution.