To disable the iPhoto screen saver from showing your albums try this:
1.) Launch the Terminal application
2.) Type the following command (all on one line) and hit return
defaults delete com.apple.iApps iPhotoRecentDatabases ; chflags uchg ~/Library/Preferences/com.apple.iApps.plist
I have done this on my computer and have not noticed any ill effects from it. Essentially the command deletes the "iPhotoRecentDatabases" key from the "com.apple.iApps.plist" preference file and then locks the file so iPhoto can't write back to it the next time you launch iPhoto.
If you do experience any strange behavior after trying this you can unlock the "com.apple.iApps.plist" file in the Finder's "Get Info" window or you can issue the following command in the Terminal application:
chflags nouchg ~/Library/Preferences/com.apple.iApps.plist
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