You must have an NVidia gpu. Either create a steam account or add to your existing one.
http://www.steampowered.com/nvidia/#
Don't bother if you own the Orange Box you won't get anything added. Make a new account and lend it to your friends =P
http://www.steampowered.com/nvidia/#
Don't bother if you own the Orange Box you won't get anything added. Make a new account and lend it to your friends =P