I just thought I'd mention this in case others are having similar issues running GP4 on windows 10 computers which have more than enough CPU, memory and graphics power (in theory) to run GP4.
I posted not too long ago thinking the slowdowns during races (almost to a stop sometimes), might be due to GP4 tweaker or maybe team editor - maybe even the size of car wads with the latest cars and tyres.
I tried adjusting everything I could think of to reduce the high processor occupancy which was there during every slow down
Thanks to an older post from Excalibur I seem to have found a solution which is to use CFF Explorer to open and edit the GP4.exe to remove the 2GB memory usage limit. As soon as I did this the processor occupancy is 60 to 70 at the start of a race and then drops to 50 or below for the remainder of the race. Finally GP4 looks like it did on Windows XP!
Apologies for those who may have done this already but if you are having slowdown issues on newer PC's, you may want to give this a try -
SLOWDOWN SOLUTION
Allow GP4 to handle more than 2Gb address space with CFFExplorer (Open gp4.exe with CFFExplorer, into "file header" , into characteristics, click on "click here" and into the options, tick the box: "App can handle more than 2GB space adress". Then save your gp4.exe)