Halo: Reach fans who intended to play it on the new 4GB Slim Xbox 360 were on to a little surprise: they can't play the game in co-op mode.
As reported by several users, when trying to start co-op play with one of the players using a 4GB Slim Xbox 360, the players get an error message stating that "one or more players do not have the hard drive required for this game type."
The hard disk requirement is not stated anywhere on the game's box; however the first item on the game's FAQ site reads as follows:
Q1: The error "One or more players do not have an Xbox 360 Hard Drive. An Xbox 360 Hard Drive is required to play co-op on Xbox LIVE or system link" occurs when I try to play. Why?
A1: One or more players do not have a certified Xbox 360 hard drive attached to their Xbox 360 console. Some multiplayer aspects of Halo: Reach require an Xbox 360 certified hard drive.
It is worth noting that adding a USB drive doesn't solve the problem.