Re: Rendered Mpeg2 720p doesnt play on other system.

OK, so it ain't the HDD (and suggesting 24p to save 20% on the data rate won't help... dangit!).

DivX might do the trick. Worth a try. For the same data rate you'll actually get better quality with DivX flavored H.264 than MPEG-2, but if it's some sort of processing issue, then - because DivX is more computationally intensive - you'll have more problems. Anyhow, it might work. There are other MPEG-4/H.264/AVC options with an AVI wrapper as well.

There seem to be a lot of video players (most? all?) that will do what you want, but I'm not sure about presentation apps. The church industry has some good ones, like MediaShout (which was my first suspicion on what you were using, because I've seen lots of video file compatibility issues with that software over the years).