You say you are using a nocd patch... Is this the 9.6 official patch version or original GP4 version? If the nocd is for the 9.6 official pached version, the GP4.exe calls some *****.tex and some collision mesh files from a directory that the official patch creates when it is installed. ie Program Files/Infrograms/Grand Prix 4/Cars.
If you have not installed the 9.6 patch you will not have these files and this directory, but if the nocd is compatible with 9.6 version the GP4.exe will look for them. When they are not found, result... crash to desktop.
This may not be your problem, but I thought it worth mentioning. I run my GP4 with hyperthreading enabled and no probs...