Having solved the changing of the AVI format to that needed for the Archos - I've gone on to trying to record from T/V. Now, I can get a video signal to the machine and it will record properly - but with no sound.
I am using an S Video cable from the DVD recorder to the Archos docking unit and cables to the red and white sockets. If I plug the sound cables into the AV in socket on the docking unit - I get sound but no picture. With it disconnected I get the picture but, of course, no sound.
I hope that someone has come across this problem before as the picture is perfect - if only I had sound too :-(