Microsoft KB Archive/318691

= BUG: An absolute pointing device may cause system instability when one or more MS-DOS boxes are open =

Article ID: 318691

Article Last Modified on 9/27/2005

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APPLIES TO


 * Microsoft Windows 98 Second Edition
 * Microsoft Windows 98 Driver Development Kit (DDK)
 * Microsoft Windows Millennium Edition
 * Microsoft Windows Millennium Edition Driver Development Kit

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This article was previously published under Q318691





SYMPTOMS
When you use an absolute pointing device, such as a touch pad, switching focus may cause system instability. The problem occurs when one or more MS-DOS boxes are open.



CAUSE
The problem occurs because Vmouse.vxd does not correctly handle absolute pointer messages.



WORKAROUND
There is no known workaround.



STATUS
Microsoft has confirmed that this is a bug in the Microsoft products that are listed in the &quot;Applies to&quot; section.



MORE INFORMATION
Vmouse.vxd does not zero the event handle when an absolute pointer message is processed. Vmouse.vxd interprets the event as &quot;always pending.&quot; The problem occurs even though the event has been handled. When a Set_Device_Focus message is received, Vmouse.vxd tries to cancel any outstanding events for the old focus virtual computer. This is a problem because event handles are reused. If the event handle belongs to a different system component, Vmouse.vxd incorrectly tries to cancel the event of the other component. This causes system instability.

Vmouse.vxd does zero the event handle when relative pointing messages are processed.

Steps to reproduce the problem

 * 1) Start System Monitor. Monitor the CPU usage.
 * 2) Open two MS-DOS boxes.
 * 3) Use the touch pad to change focus between the two open MS-DOS boxes. Do this at the same time that you are typing.

Notice that CPU usage jumps to 100% and stays there.

Keywords: kbtshoot kbbug kbqfe kbddk kbhotfixserver KB318691

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