iphoto 7.1.5 slideshow not working

I am using Iphoto 7.1.5 on a Mac OS X 10.6.8 for my photography business, which allows me to download different clients photos and play them in a slideshow. However, the slide show option will not work any more. It allows us to play the slideshow and music but no photos show the screen stays black. Also, it will not allow us to preview the photos after they are imported unless i use full screen! I tried to uninstall and reinstall but im not sure how. Any help would e much appreciated!

Thank you!