if it saves as, or renders .gif then it might work.
remember, 64x64 pixels max on avatar. movie maker might not output that small, or if it does, it might look not look good. you can do a search for free gif animators, that will crop it to the right size.
theres a lot of gif animators out there, most leave a watermark. i tried a few, before i found one that just had a time limit, without the watermark.
good luck

Scarz a.k.a. Scarakus
New Mirror http://scarz.altervista.org/Index.htm