Since the original master servers are often down, you may need to use a Community Patch (like the 1.51 patch) to see active servers.
: If the game is already installed but asking for a key, you can often "fish it out" of your system’s memory. Press Win + R , type regedit , and hit Enter. cod united offensive cd key
If you purchased the game digitally on platforms like or GOG (Good Old Games) : Since the original master servers are often down,