Not to sound modish but.. you have two threads witht he same question. anyways do you have a valid copy of Halflife and Steam and a HalfLife cd key. Register you HalfLife cd key with Steam and then Play HalfLife once and then Download and install ESF. That should work. If you have already done all of those things then uninstall them all and then re-install them and make sure that you get the 1.2.3 FULL Install.