If you are looking to get your hands on Half-Life: Opposing Force today, you have two primary routes depending on whether you are a digital gamer or a physical collector. 1. The Modern Digital Route (Recommended)

The key is permanently tied to another Steam account.

A: If you purchase the game digitally on Steam, no CD key is required—the game is tied directly to your account. If you are installing from original CD media, a valid key is required.