I've resolved my white Ferrari...!!!
As I mentioned I only experineced this when using dercypted exe file for patch 9.6. The reason.....was because the official patch was not installed correctly at all..!!!. I'll explain in detail just in case anyone else has the same problem.
I originally installed GP4 onto my second hard drive with the following directory path, as I like to install games where I want them, not where the game wants to (which I think is C:\Program Files\Infogrames\Grand Prix 4)
d:\Grand Prix 4
All was fine, then I obtained the zipped self extracting Offical patch 9.6. When you extract this file it wants to extract files to the directory C:\Program Files\Infogrames, and will in actual fact create a new directory with the patch setup files in a new folder called "GP4_Patch v96".
I however origianlly installed to D:\Grand Prix 4, chose to extract the new patch folder to the root of D:\, using winzip. When I then ran the setup file from within the new patch directory, it stated that the game was successfully patched, but it had actually created a new directory called "Grand Prix 4" on my C:\ drive, which had all the patched files in it....grrrrr. Result was that files in D:\Grand Prix 4 where I ran the game from were not updated at all...!!! So when I used the 1.02 decrypted GP4 exe, it was not the right file as my actual game was still unpatched....!!!
I managed to resolve this by uninstalling then re-installing GP4 to the directory D:\Infogrames\Grand Prix 4, and getting the zipped patch to extract the new folder to D:\infogrames. Running the patch setup was then successful.
Then using the new 1.02 decrypted file was fine with no more white Ferrari.