Go onto the main Grand Prix 4 directory, C:\Program Files\Infogrames\Grand Prix 4\MenuData\PC\GP2001, theres a file called GP2001_English.gps, open this in notepad, scroll down to track names, or search for them then rename them in whatever way you want. Save and voila it will be in the game. If you use another language then use GP2001_Deutsch or whichever language is yours
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For a list of EVERY download for GP4, look here: [docs.google.com]