Most software is not backward compatible, this isn't something specific to Macromedia. You can't open Corel Draw 9 or 10 files in 8, and that goes for a lot software. You can open 8 and 9 in 10. That's just how it works. They would have to add patches on patches to make the old stuff accept the new formats--and then why would anyone want to upgrade. It's like trying to play a cassette, 8 track or lp in a cd player.