If your having problems with System Preferences, it might be it's Preference file, which reinstalling the System Preference program will make no difference.
First locate the com.apple.systempreferences.plist file in your "Username"/Library/Preferences folder and drag it to the Trash.
Reboot and startup System Preferences, see if it works and if it does, reset your preferences.
If System Preferences still doesn't work, the do #8 Reinstall Only OS X, which will replace the program, then Software Update fully to get current.
(note: if you not on 10.6, then follow the link above to find the method for deleting the file in 10.7+)