Travel Technology - What is the video format which the most computer users can play?

And what bit of software should I use to convert videos to it on a mac? I need to provide a bunch of people with a powerpoint which contains a video, and a separate video only file. At the moment, some people on PCs are having problems (the video is an .mp4 and the file in the powerpoint is a .mov). I'm very ignorant about these things (and quality / file size not an issue, the most important thing is it being able to be played by the most number of people when they put the disc in their machine).

MPEG 1 (http://en.wikipedia.org/wiki/MPEG-1) (.mpg)

I would agree. .mpg is bigger but is probably the most compatible.

Bigger is fine as the files are being supplied to users on CD. I'm not having much luck in finding shareware / freeware to do the conversion on Mac OS X, so I assume that Toast or something will be my friend?

If http://media-convert.com/ can handle Mac file header formats, you're good to go.

OK, well using VisualHub I've converted the MP4 files to MPG files, but those files won't play on QuickTime or RealPlayer. Only VLC will play them on my Mac. Have I done something wrong or is there truly no close to universal format?

OK, well using VisualHub I've converted the MP4 files to MPG files, but those files won't play on QuickTime or RealPlayer.Did you convert into MPEG 1 (AKA VCD) or MPEG 2 (AKA SVCD)?

Here is a sample MPEG 1 clip:
www.purpleville.pwp.blueyonder.co.uk/rtwebsite/titleseq.mpg

Ah. I think you may well have hit the nail on the head, and I may have checked the wrong box. Seems to be working now - many thanks.