Using a local Fully Referenced URL will almost never work on other people's machines because you have no control over where they will place the published release of your story on their hard-drive.
I strongly suggest you continue to use the relative URLs and to use the Publish to File option to test either the playing of your audio files or the layout of your visual media.
But If you really want to switch to using local fully referenced URLs in your story testing then I suggest you create a story variable to store the first part of the full-reference and then to use that story variable when stating where to find the media.
<<set $testPath to "file:///c:/Users/Phayden/">>
<<cacheaudio "mememe" `$testPath + "Desktop/Psycho/Me!Me!Me!.mp3"`>>
... and then changing the value of the story variable to an empty String before you release a version to the public.
<<set $testPath to "">>
Doing it this way has two positive outcomes:
1. You only have to reset the first part of the fully reference URLs in one place.
2. You are more likely to remember to do that change before every release.