Premier showing of a documentary. Media is DVD burnt on computer. Owing to a few hiccups during preview (it stalled then resumed), the producer's helper switched to the backup disc. He watched it a while and decided it was OK. Just in case, I loaded the original disc into the laptop that was connected to the projector. I figured that I'd start it a little after the main, so if the main froze I'd just switch projector inputs and we'd be back in business. Showtime! I hit play, and the disc was 2/3 of the way into the show - the helper jughead had paused it and not cued it back to the start Knowing it would be faster than futzing with getting back to the beginning of a disc I did not know, I switched inputs and started the disc in the laptop.