Hard Reset HTC One M8 for Windows

First method:

1. Power on the device.
2. Next go to Settings -> Backup & reset -> Reset phone -> Eraase all data.
3. Confirm your choice -> tap OK.
4. Done!

Second method:

1. Switch off your device.
2. Then hold the Volume Down button for 5-10 seconds, and briefly press the Power button.
3. Next release the Volume Down button when a new icon appears on your screen.
4. Afterwards press the following buttons in sequence: Volume Up -> Volume Down -> Power -> Volume Down
5. Good job!

WARNING !
Hard Reset will erase all of your data
All described operations you are doing at your own risk.