Newbie needing help!

[slow-mo-panda.livejournal.com]

Hi, I'm new here. I was looking for a community where I could ask this question. I use Windows Movie Maker, it's the only thing I have. Does anyone know how I could make a clip move in slow-motion? I have a short clip I want to make longer by slowing it down. If anyone could help, I'd be very thankful!
I make songvids of Alan Rickman and Professor Snape, they can be seen on my website: http://www.geocities.com/slow_mo_panda
Thanks!