Hp 6220's freeze up until a little pressure is applied..

I have 3 different hp compaq 6220's all three with the same problem. Freezes up until I press down a little over the hard drive next to the mouse after I pressed down a little on it everything works fine. So if I lighten the pressure over the hard drive it freezes again. It is not the hard drive have tried several different systems with these hard drives on these three and no problems on any other system but these. Saw a forum were they said you would have to short out something on the board but I can not find the forum anymore.. VERY FRUSTATED THANKS........