cs cd key問題

我dl左dcoo cs1.6....好多server都玩到..
但係有d server就會彈句"invalid cd key"出黎...點算呀??我要解決方法呀唔該!![唔好同我講叫我唔好入= ="]

{我試過AAAAA個個..又試過數字...佢就係入唔到某D SERVER....}