I rendered a partial file and the played it in Windows Media player, just to test the quality before the fianl render. I then rendered the whole file with the same name and when I viewed it in Media Player it said the length of the clip was the same as the intial partial render Not even a reboot would convince it otherwise although it did actually play the whole file. The only way I got round the problem was to rename the file and then Windows Media Player picked up the correct file length.