- last post: 01.01.0001 12:00 AM PDT
Sure. Buy a copy of Halo PC, and on manual inside you'll find a product key. Without this key or a hacked illegal version of the game you won't be able to play.
Edit: It usually comes in the form of a few numbers/letters EG XXX1X-XX11X-1XX1X-111XX-XXX11
[Edited on 3/14/2006]