Windows Media Centre

I am trying to create slide shows in Windows Media Centre. I select the appropriate pictures and selected the same time of music (eg. 22 pictures at 10 sec each - selected 2:20 song to play), but when I play the slide show the pictures and music do not match, the pictures either loop over or the music stops before the pictures are finished playing. How do I change the settings on the pictures to only play through once and stop at the last picture and how can I time the music more appropriately?  Help please someone!!