What is wrong with my treadmill, is it an expensive repair?

I have a Roger Black treadmill which (like a lot of fitness equipment) was hardly used and has stood collecting dust for a while. When I recently decided to put it to use I found that it would only run for 5 minutes or so before cutting out - it will run again once cooled. I am not sure which componant is likely to be faulty, the motor, the cooling fan or the sensor which regulates it. Can anyone help?