Handbrake is an open-source program (free) that converts video.It is available for PC, MAC and Linux platforms.
I discovered Handbrake when I was converting PowerPoint presentations to video for iPAD distribution. The PowerPoint Save and Send as Video function converts the PPT to a WMV file. I used Handbrake to convert the WMV to MP4 format.
Start by selecting your source file (or files). Handbrake scans and sets up the GUI for the selected source file. Select your destination and configure the output settings. Choose a preset from the Preset list. This will automatically set up the all the required settings. Press the "Encode Video" button. If you have a source with multiple titles, you can queue these up using the "Add to Queue" button.
Check it out:http://handbrake.fr/index.php