how to convert .rmvb to .avi files

well i have a problem doing that, and for u who will say that it doesn’t improve quality. I need to convert it for another purpose....i have found a program out there but it costs about $30 and i only need it for one conversion, so i’m looking either for something open source, or anything else that is freeware....
if you know of anything like that please email me at: roman5566@hushmail.com
i’ve searched high and low, and i can’t find anything for that, and i’m usually good at finding things, so if you find something that will do it i will call u my master (hehe..jokingly)

thanks to anyone with any info.

http://www.boilsoft.com/rmconverter.html

eo video rmvb to mpeg or avi divx