|Turn it over on it's back and look for a small hole about 1in from the diagonal right corner of the data plate. |
Stick a tooth pick or opened-up paper-clip in that small hole, gently push it in and hold for a few seconds while the A/C power is connected and switched on.
This will re-load a fresh copy of the operating system from the on board chip where it is stored.
You may have to try using the reset button several times before it does it's job.