I have the same problem, but when I click install all, my USB mouse gets deactivated. Is that the only way? I cant really test it because well, I cant really click on stuff without my mouse.
I had the same problem, I was using Windows XP 64-bit though.
I solved it this way:
1) Plug in an Xbox controller via USB, then download the Xbox controller driver/software from Microsoft website (Google it). Install the driver.
2) Remove the Xbox controller, then plug in the PS3 controller.
3) Run MotioninJoy, click on the Driver Manager tab, check-mark PLAYSTATION(R)3 Controller, click load driver.