Suddenly everything seems to be gone.

We are using Windows7 with three users. Suddenly when one of the users logged in the system said "Preparing the desktop". After a long time the system seems to be ready but the desktop looks different from normal and all files seem to be gone.

We restarted the computer and after that everything was back to normal. What might have caused this kind of error? Only one of the three users had this problem. Nothing unusal had been done with the system.

Hello Brink,
Thank you for the answer.
I will mark the problem as solved because the immediate problem was solved by a reboot this time. But it looks as there is a lot to read and try to understand in the answer. It was very unpleasant when it happened and I really want to understand the reason.

Many thanks and best regards,
Sijon