To erase a Windows Surface Pro device:
- Plug in a USB keyboard to the device.
- Power on the device and let it boot to the Windows login screen.
- Press the power icon on the bottom right corner of the screen. Hold down left shift key and select restart.
- The device should reboot into a blue "Choose an Option" screen
- Select "Troubleshoot" -> "Advanced Options" -> "UEFI Firmware Settings" -> "Restart".
- UEFI firmware setup screen should show up. Make sure that "Secure boot control" is disabled and save the settings.