I put this as "in general" because it seems to be with all the trainers.
I'm completely stumped on this one. All the other trainers I've used from this site work flawlessly, without any compatibility mode needed at all. However for the past week I've been messing around with the CNC 3 1.9 trainer. I've been through the trouble shooting guide over and over. I'm begenning to think it's just something to do with Windows 7 x64 that I'm over looking. I've tried adding it to the DEP mode. I've used all the different compatibility modes from Windows xp SP2 and up. I've ran it as admin. I've even ran both the game and the trainer in the same settings.
For some reason it'll detect cnc3game.dat and say that the trainer is ready, but it doesn't respond to key strokes. I've even tried changing the key bindings, and I had problems with that program too. I just find it odd that RA3's trainers work flawlessly on this computer and yet CNC 3's doesn't.
Maybe someone can enlighten me on this one. >.>
Edit: Oh... I've almost forgot. I even completely uninstalled and reinstalled CNC3 as well as re-downloaded the trainer. and the 1.7/1.8 trainer as I tried that one too while running CNC3 at version 1.8.
I finally pinned it down to one thing. It seems every trainer that does not require you to press F1 to activate it doesn't work for me.
I'm having the same issue. I have a windows 7 ultimate x64 and I couldn't seem to find a solution to make the trainer work outside using my dual boot and going back to vista. I'm hoping they will update the trainer when and if they do another update for this game.