There are several ways of booting a Windows system into Safe Mode. But if you're no longer able to boot into the system to turn on Safe Mode, and the system doesn't automatically boot into safe mode, you're usually only left with a single option: using a Windows Installer USB or DVD/ISO to enable Safe Mode.

To accomodate this, you'll need a bootable USB-key, DVD or ISO image (if you're running a VM).

Start up the system, booting from the bootable media. Because you already have Windows installed, you will need to hit Enter in time to boot from the bootable media.

When Windows Setup has started and the button "Install now" appears, click on the Repair your computer link at the bo  ...