Read the following from a previous question.
How long is the full path to the audio file? Does it exceed 128 characters in
length? Try moving your presentation and all of the linked files to a new
folder - - for example C:\Test. Then delete your WMA and then reinsert it
from
it's location in C:\Test. Does that now cause it to play? There is a known
limit to the length of linked media files in PowerPoint 2003.