I moved to a different PC and logged in and opened up outlook2000.
There was an error message saying that one or more of the rules could not be run so would be disabled.
I looked at the rules and they were all disabled, not only that though, they were all 'check for text in message and move to folder type rules' which had all their destination folders removed.
I corrected all the rules and enabled them. Logged off and returned the next day to my usual pc and the same thing had happened.
The strange thing is that all the new email had been moved to the correct folders before the error msg saying the rules had been disabled popped up on my screen.
I have searched this forum and found nothing similar.