I have a 1997 ford prelude when i drive it the overdrive come on by it self do anyone know why?

Ford doesn't make a Prelude, but Honda did. If it has an overdrive on and you push it, you will not have O/D when it says O/D off. The car will default when you turn the engine off. Only push the 'O/D off' on if you're going up a hill and the transmission is continuously shifting from 3rd to 4th and back again. This function is primarily there to keep your transmission from wearing out or overheating. If you normally drive on flat land, leave it alone.