Try the following
Soft Reset-
Hold Vol- & Pwr until the device shuts down
When the device vibrates and starts to reboot, release ONLY Pwr button, still holding the Vol-
When you see the (!) on your screen, then release the Vol- button and wait until the device boots.
Your device is now soft reset
Hard Reset- (THIS COMPLETELY ERASES ALL DATA ON THE PHONE, BACK UP YOUR DATA FIRST)
Hold Vol- & Pwr until the device shuts down
When the device vibrates and starts to reboot, release ONLY Pwr button, still holding the Vol-
When you see the (!) on your screen, then release the Vol- button
Immediately, in sequence, tap Vol+, Vol-, Pwr, Vol-
The device will show gears and begin wiping the device to a factory restored version.
Device will...