As you already know, I like to run as a non-admin. What were iD thinking? The only reason the game doesn't work as a non-admin is that they try to write the config file and save games to \Program Files\Doom 3\base\, which you don't have access to as a normal user. Would it really have been that hard to save it to \Documents and Settings\<username>\Application Data\Doom 3\? No, it wouldn't have been hard, but due to this little bit of laziness, you have to be an admin and everyone on the machine gets the same settings and save games. Sigh.