If the music does not stop at the end of the slideshow, and you have selected a music file or folder for your slideshow music, then you may need to uninstall and reinstall Window Media Player 10 (or later). 

This was been reported after upgrading ProSelect on a Windows XP which had Window Media Player 10 installed and was rectified by this action.
A computer with Window Media Player 9 apparently did not have this issue.

Here is the current link (for the latest and older versions) to the Window Media Player Download Centre for your convenience (this may change in future).