I was assisting a friend of mine in making CD backups of his owerpoint presentation this past week. I was to Fed Ex them to is hotel as a double protection in case his program got stolen or damaged.
A very interesting thing happened. He was emailing me the files to burn on CD for him and many of his photos were not showing up. I kept getting the message on the bad slides, "QuickTime and a Jpeg decompressor needed to view this slide" I already had Quicktime on my computer and never have any trouble looking at jpegs.
He had produced the presentation part on a Mac and Part on a PC and had thoroughly tested the entire presentation on both the Macs and PCs he had in his office. It's still a mystery what actually happened, but to fix it he had to open the photos I was having trouble with in Photoshop and then resave them.
Bottom line. It's a good idea to have a separate backup CD with your presentation on it, and it's a GREAT idea to double check those backups so you never get caught with your pants/skirt down.