Having trouble with putting music videos on my ipod...any suggestions?

I am trying to put a music video on my 30gb ipod. I can't get it to transfer over onto the ipod in a playlist, and I can't see anyplace to check which music videos to sync. If I sync manually, I can transfer the file over, but then when I play it on my ipod it only plays as a song, and not a video. I'm really confused. Any help would be GREATLY appreciated.