techie question video formats

Hello, techie-knowledgeable listsibs,

how do I convert an mp4 file to a file compatible with powerpoint (i.e to mov or mpeg2)?

Here is my dilemma. I have downloaded a youtube clip in an mp4 format. Powerpoint does not recognise this format. My Apple does not recognise avi. So the format I need for my Apple-run Powerpoint is Quicktime's mov.

Can anyone help?

Thank you! *is going spare here*