Nothing free and easy to use that i have found. You can use a mixture of free apps to achieve it. Graphedit, virtudub and tmpeg. Using those 3 will allow you to completly decompress the wmv and then put it back together in the format you want. There may be some lose of clarity though. Take a look at this site, they have loads of gumph on how to convert video formats
http://www.videohelp.com good luck
