If you have the game installed but lost the physical key, it is historically stored in the Windows Registry under: HKEY_CURRENT_USER\Software\Valve\Half-Life\Settings in a file or string named "Key". Modern Compatibility Half-Life - Counter-Strike CD Key | PDF - Scribd
A (or product key) is a unique alphanumeric code that the game’s software checks during installation or first launch. Its purpose is to: counter strike 1.4 cd key
For original retail boxes (published by Sierra), the key was typically found on a sticker inside the CD case or printed on the back of the manual. Technical Context for CS 1.4 Anti-Cheat Introduction: If you have the game installed but lost