Follow steps below to enable F8 safe mode boot (applies to Windows 10 and 8.1):
- Boot PC using Windows 10 or 8.1 ISO USB flash drive or DVD
- Click Next to skip the first screen
- Press Shift + F10 To open advanced Command prompt window
Type the following command to enable F8 Safe Mode boot key:
bcdedit /set {default} bootmenupolicy legacy
Type Exit and press Enter to quit the Command Prompt.