There are many ways of finding your slideshows in Photoshop Elements Organizer.
1. If you know the name of your slideshow(s), you can search for them using the Search box at the top left of the Media Browser (the area with your image thumbnails).
2. You can have the Media Browser only display projects (such as slideshows):
A: Go to Find>By Media Type>Projects (keyboard shortcut Alt+4).
B: Go to View>Media Types and uncheck all other types besides Projects.
3. If you know when you created you slideshow(s), you can limit what the Media Browser displays to that date range (Find>Set Date Range or by using the Timeline (under the Window menu)).
4. If you are in the Folder Location Display mode, navigate to this folder:
A: Windows XP - C:\Documents and Settings\All Users\Application Data\Adobe\Elements Organizer\Catalogs\PSE9\projects
B: Windows Vista/7 - C:\ProgramData\Adobe\Elements Organizer\Catalogs\PSE9\projects