What platforms Halo would eventually be released for was in a state of extreme doubt during the period between the announcement of Microsoft's buyout of Bungie and MWNY 2000. There were indications that although Microsoft was willing to let Bungie make all platform decisions, that the process of making the game the best it could be for the Xbox would be technically incompatible with developing versions for either Windows or the MacOS.

However, at MWNY 2000 Alex Seropian announced that Halo would still come to the Mac, and it was later confirmed for Windows as well.