Do the following:
1. Select the movie shape that you inserted on the slide.
2. In PowerPoint 2007, select "Animations" tab, click "Custom Animations"
button.
2.1 In previous PowerPoint versions, right-click the selected shape and
select "Custom Animation..." menu item.
3. In the Custom Animations pane, select the "play" animation dropdown box
and select "Effect Options..." menu item. The "play" animation for a video
looks like the right arrow head.
4. Select "From time" in the "Start playing" section and enter 0:15 in that
box.
5. Click OK button.
This will make PowerPoint start the video at 15 seconds instead of the
beginning.
6. In the Custom Animations pane, select the "pause" animation dropdown box
of the video and select "Timing..." menu item. The "pause" animation for a
video is like two vertical bars.
7. Select "With Previous" in the "Start" box.
8. Put the number of seconds you want the video to play in the "Delay" box.
9. Click OK button.
This will make PowerPoint play the video for that many number of seconds and
then pause the video.
- Chirag
PowerShow - View multiple PowerPoint slide shows simultaneously
http://officeone.mvps.org/powershow/powershow.html