I'm having the same issue that this person had. When I run the trainer, a cheat happens logo shows up with a message saying that it is loading trainer for HollyKing, and then I get a window asking what program I would like to open .tmp files with. Was anyone able to come to a conclusion on what is causing this? I've already added the file as exempt in Windows Defender, which is my main security program.
Literally 2 pages before I explained what to do. Here's a shortcut -> Link
I am running the latest GoG Version of the game, I get the trainer activated sound but none of the options seems to work, they all say activeated but both the xp and credits one dont add anything to it. None of the other options seems to work either.
Please verify that you have created scan exclusions in your security software for the trainer exe file and the Work folder (C:\Users\YourWindowsUserName\Cheathappens\), clear these locations
C:\Users\USERNAMEHERE\AppData\Local\Temp\
C:\Users\USERNAMEHERE\Cheathappens\Work\
reboot your PC and try again launching the trainer with admin rights.