16-bit Windows-Based Programs Support Up to 26 DDE Connections

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Article ID: 198573 - View products that this article applies to.
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A 16-bit Windows-based application, which uses many DDE connections, fails after a while when running on Windows NT. The application works correctly on Windows 3.1.


After more than 26 concurrent DDE connections have been created, an error 0x400f (a system API failed inside of the DDEML) is returned when closing the twenty-seventh connection. This problem is due to a timer, which is associated with a window, not being freed when the relevant window is destroyed.


To resolve this problem, obtain the latest service pack for Windows NT 4.0 or the individual software update. For information on obtaining the latest service pack, please go to:
  • Windows Service Pack Center -or-

  • 152734 how to obtain the latest windows nt 4.0 service pack
For information on obtaining the individual software update, contact Microsoft Product Support Services. For a complete list of Microsoft Product Support Services phone numbers and information on support costs, please go to the following address on the World Wide Web:


Microsoft has confirmed this to be a problem in Windows NT version 4.0. This problem was first corrected in Windows NT version 4.0 Service Pack 5.


Article ID: 198573 - Last Review: November 2, 2013 - Revision: 3.0
Applies to
  • Microsoft Windows NT Workstation 4.0 Developer Edition
  • Microsoft Windows NT Server 4.0 Standard Edition
  • Microsoft Windows NT Server 4.0 Enterprise Edition
kbnosurvey kbarchive kbhotfixserver kbqfe kbbug kbfix KB198573

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