Your presentation plays back OK on your PC, but now that you have burnt it on to CD the video/audio clips no longer play. 

When you import video or audio clips into PowerPoint it just creates links from your presentation to the video/audio files. It is really important that when you burn your presentation to CD-ROM that you also burn the video/audio files on to the CD as well and that their relative postion to your PowerPoint file remains unchanged, otherwise the PowerPoint file will look for the video/audio files in the wrong place.

The easiest way to achieve this is prior to creating your presentation collect together in one folder all the video and audio files you are going to use. Then create your PowerPoint presentation in the same folder. 

When you come to burn the presentation to CD-ROM, burn the folder’s complete contents on to the CD, in that way your PowerPoint presentation will retain its relative position to your media clips and hence will know where to find them.