Generally when your device because unresponsive, or doesn't power on, it can be reset following these instructions.
Using a reset tool like a small straightened paperclip, insert your tool into the reset hole (located to the right of the volume keys on the T-100 series, and next to the power button for the R100 series or T301), and gently depress the internal reset button, but keep it depressed.
In the T400 series, there is no reset hole. To reset these units, press and hold the power button for at least 10 seconds.
You will know you have done this properly as the screen will go black. After holding for 30 seconds, release and allow the unit to load fully.
If unit does not turn on, you may need to press the power button.