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.