A WMV (Windows Media Video) file is a compressed file format from Microsoft. It contains video and audio information that can be decoded and played back on a video playback program such as Windows Media Player or RealPlayer. Download the Windows Media 9 encoder from http://www.microsoft.com/downloads/details.aspx?FamilyID=5691ba02-e496-465a-bba9-b2f1182cdf24&DisplayLang=en
Then just follow the wizard through to convert a file selecting either variable or constant bitrates/bandwidth depending on your needs.
You can use The Blaze Media Pro software. There are a good number of such kind of software are available as freeware and as shareware. Use google for find the best one for you.