Give
SUPER Media Converter a try. I'm not going to lie, it's a royal pain navigating through their website to actually download the program, but once you get to the download it's all smooth sailing. Basically, the program is a GUI for many of the open-source video encoders, like ffmpeg.
It'll handle just about any imaginable format to just about any other format, as long as you have the codecs installed on your computer.
Also, I second Sean's inquiry about WMV, as there are much better (and more modern) video codecs like h.264 (which can be put into AVI, MPEG4, or MOV files). h.264 may take longer to encode, but the file sizes will be smaller while video quality will be higher.