HTC One M8 Prime hard reset using buttonsBe sure to back up any data and files you want to keep before you do a factory reset
Performing a factory reset using hardware buttons
The Fast boot option in Settings > Power must not be selected
If you can’t turn HTC One M8 Prime Android phone on
1. Press and hold the VOLUME DOWN button, and then press and hold the POWER button.
2. Wait for the screen with the three Android images to appear, and then release the POWER and VOLUME DOWN buttons.
3. Press VOLUME DOWN to select FACTORY RESET, and then press the POWER button. All data will be lost!
Restores your phone to its original state.
HTC One M8 Prime hard reset from the menuPerforming a factory reset from settings
1. Go to Settings, and then tap Backup & reset.
2. Tap Reset phone.
3. If you want to delete media, documents, and other data from the phone storage, select Erase all data.
To also delete media and other data from your storage card, select Erase SD card.
4. Tap OK.
HTC One M8 Prime soft resetIf HTC One M8 Prime does not respond when you touch the screen or press the buttons, you can still restart it.
Press and hold the POWER button for at least 10 seconds, and then release it. HTC One M8 Prime then restarts.