You can set up your crontab to automatically, convert your wmv files.

1)Set up crontab
#crontab -e

Using your editor add this lines

*/10 * * * * /usr/bin/lynx -source http://www.yourdomain.com/convert_wmv.php

Where yourdomain.com is the url of your where your script is installed.

This will set up your script to run the conversion script if needed every 10 minutes.

To manually run this command anytime, just type in your browser - http://www.yourdomain.com/convert_wmv.php