Counter Strike 1.6 CD Key problem

[Agoodname22]

Hello everyone, I have a quick question regarding a copy of Counter Strike 1.6 with several other Valve multiplayer games such has TF Classic. I had this game installed on my pc and registered the product key. Today I decided I would try installing the game via steam with the CD key but it says that the product key I entered (half life platinum collection) had already been used. Is there anything I can do to get my game to work right?

[gwait]

If you activated it before, then you probably used the CD key on another Steam account before (or your current acount). Once you activate a product key on Steam, it stays connected with the account you activated it on.

[Agoodname22]

When I installed the game I didn't use steam. I think this collection I have was released before steam, but I did register the key before for authintication.