If viewing slideshow movies in Mozilla FireFox, you may need to install the Windows Media Player plug-in for FireFox. It's easy and free.
Just click here and follow instructions to install.
If you have trouble viewing some of the slideshows in Windows Media Player, trying downloading a free Xvid codec file at http://www.xvidmovies.com/codec.
You may also want to download a free DivX file (http://www.divx.com/divx/windows/) if downloading Xvid codec won't work.