This is what worked for me;
1. Find a heavy duty rubber band or some electrical tape that can hold the power button down for a long time.
2. Disconnect the power supply
3. Have the band push on the power button until the PC turns on
4. Leave it running for a long time to completely drain the battery - 10 hours or more
5. Once it is completely dead, remove the rubber band
6. Plug in the power supply and wait 20 minutes. You want to see the light steady orange at this time
7. Turn the PC on with normal 2-second push on power