Lizard Protector viewer will play unprotected mp3 or mov files, as long as the path is correct.
You need to use an absolute path when calling a mp3 or mov file (so instead of trying to load /audio/file.mp3, use http://domain.com/audio/file.mp3).
This is because mp3 or mov plugins can vary (unlike flash files, where you have to use the Macromedia plugin) and they may not properly handle a relative path (given that the protected HTML file loads from memory).
The problem with mp3 and mov files is that a customer may not have a plugin for playing them, while the flash plugin is installed on the vast majority of Windows computers. Also, you cannot protect mp3 or mov files using Lizard Protector.
So, your best option is to convert the files to flash and make sure the file sizes are as small as possible. You can then protect the flash files.