According to my records, the course ID and Key are the following:
ID: 0ceb653f438a4030ae217d528da14729
Key: 47fc771e2b582b4b67e1e9899b370262
I don't know what is wrong, but I am investigating.
This is the file. It isn't zipped so put it in your /Links 2003/Courses/ folder, but remove any other Old Head .CRZ files that are in there before you try to open the game.
https://www.dropbox.com/scl/fi/egzdylijnwvcwy0rd0rqm/OldHead-GC-HD-Final-1.CRZ?rlkey=wrpgdo3hp30i70xlomxz8o96b&st=qco6xf9w&dl=0Pete