Status Date and Work Shown to be Perfromed Before

Can someone explain how MS Project 2003 calculates the start and finish dates for the activities scheduled to start before the status date, BUT HAVE NOT STARTED. When I tested this start and finish dates would still be before the status date and the predecessor relationship WAS IGNORED. For the activities that have started when a right option is selected remaining work is shown after the status date, which was correct.

Can this be explained and is it any way that an activity has not started can be “moved” after the status date?

Thanks,