I just love the application "SUPER".
It can convert pretty much anything, and it is completely free, and often updated. I have converted tons of files, and the only time i ever needed anything else, was when i had to split a GIF animation.
Get it here
http://www.erightsoft.info/
(for some reason it always takes forever for me to find the link to the setup, but it's there)
Good luck
Keba