Thanks "shuttle" for your advice. As it happened, I was just about to try and install GP4 Master.
I did eventually get the exe102 decrypt file to work along with the Lap/Pit Editor and the cmagic_102 utility. From their, the performance update worked, although it changed many seetings (e.g. my steering wheel configuration) and everything seemed forgein to me. The only perceptable difference was that the cars seemed to go faster although I only had about one lap. So I thought I would try to get some new cars in and change the driver names to get the full effect of all the updates.
The cars I downloaded needed to use GP4 Master, so I downloaded that.
Could I get it to work??? Of course not. It needs to be linked to a certain file - a decrypted file which it said I did not have. But did have it. I could play the game without the CD so must have had it.
So I came back to the forum and found your very helpful message (above), but I could not go back to save any other versions of GP4 as everything had been installed up until that point. The only thing I could do was start all over again. Uninstall, reinstall and reload everything bit by bit.
I have now tried to rename my "original" GP4 file at every stage in the procedure but with no luck. GP4 Master is asking for the "unencrypted GP4 file" which has to be exactly "6,250,496 bytes" in size. At no stage can I find a GP4 file to match that size.
What the hell am I doing wrong! Are their no instructions for this kind of thing? I may have missed something in your translation "shuttle", but I think I did what you said correctly. I have now spent about 16 hours trying to get this stuff to work but I seem to be stumbling around in the dark.
Could anyone please help. If I get GP4 Master working I may be over the last hurdle and on the home straight.
Thanks for listening.
Dave.