Thanks, I have looked at both Smartmovie and another piece of software called Mobile Movie Maker. Both only seem to support avi files. These are great in their own right but I find the 7710 falls over on anything other than the lowest of settings.
Discussing this with a few firends of mine who already own the 7710, we all agreed that with regards to playing video on a hand held device, we have already sacrificed picture quality and so would rather make sure that we had the best sound experience possible to make up for the perceived loss of image size and frame rate.
The avi movie makers are great for allowing the end user to choose stereo sound encoding but the 7710 often falls over and stutters with this option due to the processing power needed. However, by comparison 3gp (QCIF standard) resolve a decent quality image with full stereo sound without any difficulty on the 7710, and hence my wish to push the 3gp format further to see if full 16:9 could be rendered on the phone without having to resort to letterboxing.
It's also worth noting that real video 8 files can be made to display full 16:9 with stereo sound without problems and a piece of software called Deset Pocket Movie Symbian does this quite nicely, but the resulting files are quite large and my personal preference for the rm format doesn't endear me to it.