You have to get some codec installed there like divx/xvid and mp3 the sound to get the file size down if you dont know how to do that then do what magnatom says and wmv it.
Youtube dont care about file size as it will convert it down on there server, but what is important is if its too big it will time out on you connection time limit so get it as small as you can.
Youtube has a time limit as well so make sure its not over.
For myself I would xvid/mp3 and use virtualdub to cut.
/edit on uploads to youtube.
