They don't work at all. No "trainer activated", no confirmation sound(s),absolutely NOTHING.
Sometimes I have found you have to run the trainers as administrator. To test this out, right-click on the trainer and click run as administrator. The trainer will then open. Fire up the game and see if it works. If it does, go back to the trainer, and right click on it again and go to "properties" and click the "compatibility" tab. On this tab, tick the box next to "Run this program as Administrator" and click OK. The trainer will now always run with Administrator rights.
Hope this helps!