Your computer is trying to play back ALL of the frames, but it can't keep up (VERY few could!) with the frame rate off your CD-ROM drive. So, it plays back what it can, which makes it slower. I would use SOME form of compression for any file I wanted to watch. But, for any files you still want to edit, like compose over a live backround footage, or something, keep a copy for doing those things at full rez un-compressed. Once you compress, you CAN'T go back! NEVER COMPRESS FOR ARCHIVE! CD-R's are cheap! Fill them up! DivX is good for Windoze, but others may have problems playing back your files. My 2 cents... :>