If you do not have a physical disc, the community recommends the following sources for a pre-patched, safe version of the game:

To download and play (originally released in 2005), you cannot simply purchase it on digital storefronts like Steam or the EA App as it has been delisted. Instead, you must rely on community-supported versions or physical copies. Where to Securely Download Battlefield 2

Battlefield 2 requires specific patches and community software to function on modern Windows systems and to access online multiplayer (since the original GameSpy servers were shut down).