Halo is protected with SafeDisc 2.9 (correct me if I'm wrong)
SafeDisc 2.9 do have blacklist. Uninstall CloneCD or dissable virtual cloneCD drivers.
Same for Nero, CD Mate and BB.
Have l8est Alcohol or l8est demon tools - virtual driver installed and activated. THAN it will work!
Read about backing up and s*it in my backup guide!
Or use a no-cd like GLH says!