One of the most frequently asked questions is how to delete a duplicate entry or simply just remove a ringtone you no longer want from android's stock ringtone selector. I toyed with the idea of making a simple app with the instructions to do just that and I may still but here's the first thing you can try if you want to remove that family guy ringtone you no longer want from your phone.
Menu->Setting->Applications->Manage applications->Media Storage->Clear data, then reboot.
To see Media Storage in the list you may have to click on the All tab then scroll down to it, sometimes this list takes a few seconds to compile.
That fixes most problems and will most likely delete the ringtone in question leaving android's stock ringtones alone.