As per in the rules, following links will allow you to download all the offcial patches and updates which will enable you to join the league.

Grand Prix 4 Patches (Required)

• Official Patch v9.6 Fixes multiple bugs present in the original game.
• NO-CD Patch 1.02 Enable you to run the game without using the CD.

Grand Prix 4 Utilities (Required)

• GPxPatch Real-time extension system for GP4. It patches GP4 at run-time to change several aspects within the game and to add functionality of its own (SDI Game Utilities).
• HOFxLap It is a hotlap/game file viewer, mainly used for authentication(SDI Game Utilities).

Grand Prix 4 Carset Mods (Optionals)

• 2003 Carset 2003 medium resolution
• 2003 Carset high resolution