Read this to learn how to (forcefully) quit bugging applications or programs in Windows 8.
Force quit in Windows 8
Sometimes an application or a program might malfunction and stop responding. In such a case the old Ctrl + Alt + Del killer combination has always been there to help you in all versions of Windows. Windows 8 also brings the same legacy.
1. Press Ctrl + Alt + Del. Click on Task Manager.
2. In the Task Manager window, right click on the application you want to force quit and select End Task.
Windows 8 also asks you if you want to Force Quit in case of non responsive applications while you are Logging Off your PC.