half-life problem

[Eliminator]

everytime i try to play any half-life mods, I keep on getting a error saying "Cd Key cannot be used on Valve system". I reinstalled half-life, I put the in the correct cd key that i got with my game. Nothing seems to work. Does anybody know what to do?

 

[Glenn]

I once had this problem myself. The way that I fixed it was to install it in a different location such as a different drive. If that does not work contact Valve.

 

[Holden]

Your Cd key may have accidently been printed on 2 copies of Half-Life retail if the post above hasn't helped you take a picture of your cd key and case and email/fax to sierra