MSDN Library - RegisterHotKey http://msdn.microsoft.com/en-us/library/ms646309(v=VS.85).aspx > Remarks > The F12 key is reserved for use by the debugger at all times, > so it should not be registered as a hot key. Even when you > are not debugging an application, F12 is reserved in case a > kernel-mode debugger or a just-in-time debugger is resident.