Don,
That's a bit of a " how long is a piece of string" question.
Most of the video formats that powerpoint likes (mpg, avi) can have a "compression quality" setting applied. the most
compressed (read lower quality) movies can look awful. So it's always a trade off between compression and quality.
Cheers
TAJ Simmons
microsoft powerpoint mvp
awesome - powerpoint backgrounds,
free powerpoint templates, tutorials, hints and tips etc
http://www.powerpointbackgrounds.com