Open a command prompt with administrative privileges.
Safe Mode:
bcdedit /set {default} safeboot minimal
Safe Mode with Networking:
bcdedit /set {default} safeboot network
Safe Mode with Command Prompt:
bcdedit /set {default} safeboot minimal
bcdedit /set {default} safebootalternateshell yes
You need to remove the bcdedit value to prevent the PC from continually booting into safe mode.
bcdedit /deletevalue {default} safeboot