It is possible... though I cannot talk here about copywrites, etc., as you
are doing academics and all I know for that is business application... so:
First thing you have to do is get the clip you want to show. For the most
part this will be a simple Right Click the video or link and "Save As"
Myspace videos might be difficult as I am not sure how they are
shown/stored... basically if you can't put the video on your home computer,
or burn it to a CD you might have issues.
Video codecs and format are a whole other issue, and there is plenty of
information about that on google if you start to search around for things
like "powerpoint video" or "powerpoint mpeg".
BUT to answer your question as simple as possible:
Insert > Movie and Sounds > Movie From File
Pick your video file, and hit OK.
Now the hard part: getting the clip you want to show!