I have a problem with the key of the half-file, al to create a departure of EFZ, in the way of load leaves me that the key is I nullify. would desire to know if I have to place a key general for the half-life or enters with any??
Your style of speech gives me the feeling that you don't speak English well, and used an online translator. I can understand what you're saying, though, so I'll help you as well as I can.
Short answer: this happens when people pirate Half-Life. It's theoretically possible that someone could have obtained your CD key by random via an illegal CD key generator, but rather unlikely. So, I have to ask you - did you legally purchase Half-Life 1, or an equivalent package? If you have, and upon registering Half-Life 1, Steam rejects your CD key, there's little you can do. Valve offers a (rather complicated) service of "resetting" a CD key, but it involves sending them proof of purchase and a $10 USD fee. I believe you can only do it within the first 30 days of buying HL1, as well.
If that is truly your situation, you may just be better off buying another copy of HL1 and cursing your bad luck (or Valve). If the former situation is true, then you need to legally purchase Half-Life 1.
It happened to me when I bought Half Life, when I went to install it my CD-key was in use for some reason. I sent a proof of my purchase to Valve, but ended up just going back to the store next day and they gave me a new game instead, never got any reply from Valve. So I just suggest that if you -did- buy the game, go back to the store and tell them about your problem.