Laura,

in powerpoint - go to the insert menu
choose "movies and sounds" then choose "movies from file"

Then browse your computers hard drive to find the movie file you want to
insert

click its filename then click "insert"

then you can re-size and position the video clip on your slide.

Powerpoint can be a bit awkward on what video files it can accept... so this
powerpoint utility takes the guess work out of inserting movies
http://www.playsforcertain.com

cheers
TAJ Simmons
microsoft powerpoint mvp

awesome - powerpoint backgrounds,
http://www.awesomebackgrounds.com
free powerpoint templates, tutorials, hints, tips and more...