What 've done in tha past for screensavers:
1. Make an AVI of my movie.
Then find a screensaver utility like tariqrf said, one that can make a screensaver from avi's.
OR
2. import the frame sequence into flash, and save it as a projector movie.
Then, do the same as above using "Screenweaver".
Israel "Izzy" Long
Motion and Title Design for Broadcast-Film-DS
izzylong.com