Try these steps if your system is frozen so you cannot force quit Windows apps:
Press Ctrl + Alt + Del (or enable them), try to select one of Sign out, Restart, or Task Manager to kill rogue apps. Open Task Manager – Press Ctrl + Shift + Esc to open Task Manager; find Windows Explorer and right click on it and click on Restart. Ctrl + Win + Shift + B – This refreshes the graphics driver which may help you from unfreezing the system without rebooting. Restarts by force – If all breaks down, try pressing and holding the power button for 5–10 seconds until the machine restarts and we turn it on. Update Drivers – This helps you to make sure there are no drivers missing in your system. It also refreshes your system drivers to prevent freezing in future.