[/I]You will need to either reinstall OS X or use the app "Pacifist" to extract it from your original 10.5 disk.
Have seen suggestions that downloading/installing the latest combo update might reinstall it, but typically has not been successful.
We would know nothing about a missing plug in with out more info - what app are you using, when do you get an error, and what is the error.
Hi, Im new here. I accidently deleted my system preferences on my osx 10.508.
Hold on again. Have you searched for SP in Spotlight? Maybe you have more than one Applications folder, and you just looked in one.