Now that we have the navigation buttons on the master slide, decide what external links need to be created. Before we do that, though, we need to cover one of the biggest pains in PowerPoint: Absolute links and relative links.
On a computer, each file has a location on a storage device. This location is referenced by using a path. For example, if storing a file called KeySound.wma in the My Documents folder, the full path to the file might be C:\Documents and Settings\MyLogIn\MyDocuments\KeySound.wma. This kind of path is known as the absolute path (address).
When inserting this sound file into a presentation, PowerPoint creates a link to it. As long as the presentation is only used on the same machine, there are no problems. PowerPoint knows the path is the same and can always play the sound.
When sending the presentation and the sound file to another computer, because the path is absolute, PowerPoint thinks it will be located on the hard drive at C:\Documents and Settings\MyLogIn\MyDocuments\KeySound.wma. The login on the other machine isn't MyLogIn. Instead, it might be YourLogIn. Poof! The path changed and PowerPoint can't find the file, so the sound doesn't play.
There is another way to reference files. Instead of referencing the absolute path for the file, reference the relative path for the file. The relative path is the path you would need to move through to get from one file to another.
Relative links can be quite useful since they let PowerPoint find linked files. But PowerPoint understands only one kind of relative link: When both files are in the same folder before the link is created, PowerPoint creates and understands a relative link between the files. In other words, if the link doesn't contain any folder or drive references, PowerPoint will be able to use the link to find the file, no matter what computer the files move to. If the link contains any folder or drive references, PowerPoint can find the file on the original computer, but not on any other computer.
If the sound file is in a sub-directory of the folder containing the PowerPoint presentation, the relative link would be \KeySound.wma. This means go up one level in the folder or directory structure and find the file there. By the same token, if the sound file were in the same folder as the presentation, the relative link would be just the file name .
When linking files in PowerPoint, whether they are the sound files used up to now, or the PowerPoint and other files we are about to use, make sure all the files are in the same directory as the presentation before linking them to the presentation. Then, when the files are moved to another computer, take the entire folder and there's no need to worry about bad links.
If links break anyway, wander over to PowerPoint MVP Steve Rindsberg's site and pick up his FixLinks tool. It repairs links and ensures the presentation can still find all its files. The URL for information on FixLinks is http://www.rdpslides.com/pptools/FAQ00035.htm