Step 1: When you hit the power button in Windows 8.1 (through Charms Bar), hold down the Shift key when clicking the Restart button.
Step 2: The next screen will present you with three options. Click Troubleshoot.
Step 3: Next, hit Advanced options followed by Windows Startup Settings from the next screen.
Step 4: Your PC will now be rebooted to enable the advanced parameters, which include Safe Mode as well. Once it restarts, you’ll get nine options whereby the following commands apply:
F4 for Safe Mode