You cannot use videos as slide backgrounds in PowerPoint 2010

PowerPoint 2010 supports the playing of videos behind other slide objects during a slide show. You can use this feature in PowerPoint to work around this problem. To do this, follow these steps:

Note This workaround does not work for earlier versions of PowerPoint. However, you can use the PowerPoint Viewer to run a slide show. The most current version of the PowerPoint Viewer supports the playing of videos behind other objects on a slide.
 

1. Browse to the slide for which you want to play the video as a background.
2. On the Insert tab, in the Media group, click Video, and then click Video from file.
3. Select the video that you want to use, and then click Insert.
4. Under Video Tools, on the Playback tab, in the Video Options group, select either On Click or Automatically on the Start list.
5. If you want the video to loop continuously on the slide, click Loop until Stopped.
6. On the Slide Show tab, in the Set Up group, click to clear the Show Media Controls check box. This prevents the video controls from appearing if you move your mouse pointer over the video during playback.
7. On the Home tab, in the Drawing group, click Arrange, and then click Send to Back.

You can also add the video to the Slide Master for the presentation if you want the video to appear on every slide. However, when the slide show advances to the next slide, the video restarts from the beginning.