This function allows an application program to cause the system to lock up at any point in time. For example, a programmer might wish to lock up the system if any tampering is detected, such as a password being misspelled more than four times in a row.

In order to execute WinUnlockSystem after a WinLockupSystem has been called, the WinUnlockSystem must be called from a separate thread because WinLockupSystem will not return until a password has been entered from the keyboard.

The LockupHook hook allows a PM application to customize system lockups.

In order for the window to appear as the top most window on the lockup screen, the WS_CLIPSIBLINGS flag must be used for the flStyle parameter in the WinCreateWindow or WinCreateStdWindow call.