Notes about the XXI file extension:
Incorrect file associations could be the result of underlying issues within your PC system. As such it is highly recommended to scan your PC for invalid registry entries, unused processes and other unfavourable system settings to identify slowdown issues.
The XXI file type is primarily associated with 'GameSpy Arcade' by IGN Entertainment, Inc.. GameSpy Arcade is a shareware multiplayer game server browsing utility. GameSpy arcade allows players to view and connect to available multiplayer games, and chat to other users of the service.