Doom 3 Patch 1.3

[JettaRacer]

Alright i bought doom 3 installed all the patch everything was fine well my dad goes and messes the comp all up and he backed up the system well i uninstalled doom for some reason i forget wast i was doing well i re installed doom and i download patch 1.3 again wen the system installer comes up for the patch it says its already installed but doom says its not WHAT DO I DO PLEASE HELP!