Don't close System Preferences yet! Take a peek in the bottom section of your System Preferences window, labeled "Other". How many items are down there? Do you know what they do? Do you use what they do?

If there is a Preference Pane that you don't use or that you use only occasionally, disable it (either turn it "off" within the Preference Pane itself or remove it from the folder "~/Library/PreferencePanes").