As a result of your questions I did some more investigation. Everything appeared to work fine when done manually via the DVD2AVI interactive user interface, so I then looked for ways to make it go wrong from the command line. I have found a couple of ways to get the symptoms I had: - Use a very long path name. I guess this blows some command line limit. - Have a comma in the path name. I guess this blows up the DVD2AVI parameter parsing. Anyway, I have moved all my files to a top level folder which does not clash with the above points and it has all started working. Thanks for the questions - I guess just the fact that you could not see any reason for it not to work spurred me to look further.