help help

i hv try all the step in tis link
http://forum.lowyat.net/index.php?showtopic=194213

but still cant convert rmvb file to avi
even though i hv rename the file from 01.rvvb to 01.avi
but the file name is 01.avi.rmvb wo
so it alway show error
any other way??
i already keep on step 4-6 as require
but stil fail