Microsoft small business knowledge base

Article ID: 71850 - Last Review: February 27, 2014 - Revision: 2.1

This article was previously published under Q71850
This article has been archived. It is offered "as is" and will no longer be updated.


When running Windows 3.0 in real or standard mode, or Windows 3.1 in standard mode, the following warning message appears in a dialog box when you run any Windows communications program and attempt to start an MS-DOS application (or vice versa):

The title bar of the error message display the name of the MS-DOS application, then in the error message box it displayS the following:
Another application is using the communication port. It might lose characters if you decide to start your application now.

Do you want to start your application? Y/N


This warning message appears when you start an MS-DOS application while running a Windows communication program that uses the communication (COM) ports. The active communication program in Windows may lose data or its connection if the MS-DOS application uses the same port during its current session.

To avoid this, do one of the following:

  • Exit the Windows communications program and then start the MS-DOS application.

  • In the Windows communications program, set the port connection to none.
NOTE: Even if a PIF file is used for the MS-DOS application where no COM port is chosen to modify, the warning message is still displayed because the Windows communications program is currently using the port.

This problem does not occur in 386 enhanced-mode Windows because the programs are multitasking and the COM ports are virtualized. In standard and real mode, the Windows communication programs are suspended in memory until reactivated.

This problem has been tested with the following Windows communication programs:

  • Windows 3.0 Terminal Program
  • Dynacomm

  • Microsoft Windows 3.0 Standard Edition
  • Microsoft Windows 3.0a
  • Microsoft Windows 3.1 Standard Edition
  • Microsoft Windows 3.11 Standard Edition
kbnosurvey kbarchive KB71850
Additional support options
Ask The Microsoft Small Business Support Community
Contact Microsoft Small Business Support
Find Microsoft Small Business Support Certified Partner
Find a Microsoft Store For In-Person Small Business Support