I also just tried making the backups cd size and burning them all to a dvd. Still won't work. The burn goes fine, no errors or anything, and all the files show up on the dvd but the .exe will not execute. I've checked the backups from my hard drive and they work just fine, but once I put them on dvd, nada.
edit**
I just moved the files from the dvd back onto my hard drive and it worked. Why wouldn't I be able to execute the file from the dvd?