Untz

Hi All I have made a video/slideshow in photostage with audio, I originally had video of about 2hrs and I have deleted the excess video/slides etc down to 4.31mins - however it still runs to over 2hrs if I preview it showing a blank screen after my slideshow ends at 4.31min. There are no rogue slides or audio files causing the problem. Is there a quick and easy way to end the slideshow at 4.31min so I can export it as MP4? Any help greatly appreciated...