My co-worker brought her phone to me to look at when it had the "Do not turn off target!!!" with an Android in a green triangle. The phone would not respond to anything. I tried turning it off, holding the power button down for 10+ seconds, and nothing worked. I then took a thumb tack, pressed it in the tiny hole on the bottom, and pried the phone apart at a separation. Removed the battery, and lightly blew the dust out of the battery spot (no idea if this part helped), and replaced the battery after 10 seconds. The phone immediately began to reboot. When it asked if i would like to reboot i pressed the upward facing arrow at the bottom of the screen and VIOLA!; the phone was up and running again.