Counter-Strike 1.5 is a legacy version of the game that predates the official Steam release in 2003 . Finding a "new" CD key for this specific version is largely impossible through official retail channels today, as the original World Opponent Network (WON) servers were shut down by Valve in 2004.
: When Valve launched Steam, players with retail keys could "register" them to upgrade to Counter-Strike 1.6 for free. Most valid retail keys from that era have already been claimed and used. Current Availability counter strike 15 cd key new