What are the system requirements for Halo 3?

Halo 3 is not available for PC, it is only available for Xbox 360.

But, Halo 2 is available for PC. I can give the system requirements of Halo 2.

OS - Windows Vista

Processor - 2 GHz

Memory - 1 GB RAM, 7GB Hard Drive Space

Video Card - NVIDIA 6100, ATI X7000 or Above ( 128 MB or above )

Halo 3 is not currently available on a PC. Therefore the system requirements at this time is to have a functioning Xbox 360. If you wish to play it on Xbox live you will need internet hooked up to the Xbox 360.