I am looking for an easy-to-use and trouble-free program to convert 3GP files into AVI files and vice versa.
Karl Teofilovic
I usually use Super © for all the video conversions that VDub can't handle, and the version of Super © released on 5 January says it can input and output movies in the 3GP mobile phone format. But it's not the most user-friendly software, and you may find DVDVideoSoft's Free 3GP Video Converter worth a look. There are paid-for alternatives, of course, such as the OJOsoft Total Video Converter.
Later: Karl tried the DVDVideoSoft program and says: "I have used it a couple of times only, but so far I find it to work really well."