Running a Windows NT Communications Program with COM3 or COM4

ID: Q134424

The information in this article applies to:
IMPORTANT: This article contains information about editing the registry. Before you edit the registry, make sure you understand how to restore it if a problem occurs. For information about how to do this, view the "Restoring the Registry" Help topic in Regedit.exe or the "Restoring a Registry Key" Help topic in Regedt32.exe.

SYMPTOMS

A communications program written for Microsoft Windows NT does not work in Windows 95/98 if your modem uses COM3 or COM4.


CAUSE

In order to accommodate the method used by Windows NT for serial communications, Windows 95/98 has a registry key that identifies the COM ports. This key includes only the COM1 and COM2 ports. Modems using COM3 and COM4 are not recognized and cannot be used by Windows NT-based programs.


RESOLUTION

To use a Windows NT-based communications program on a Windows 95/98-based computer with a modem using COM3 or COM4, add the string value

COM3

to the following entry in the registry:


HKEY_LOCAL_MACHINE\hardware\devicemap\serialcomm

Set the new value so that it is equal to the string value. For example:
COM3=COM3

NOTE: If your modem uses COM4, substitute COM4 for COM3.

WARNING: Using Registry Editor incorrectly can cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk.

For information about how to edit the registry, view the "Changing Keys And Values" Help topic in Registry Editor (Regedit.exe) or the "Add and Delete Information in the Registry" and "Edit Registry Data" Help topics in Regedt32.exe. Note that you should back up the registry before you edit it.


STATUS

Microsoft has confirmed this to be a problem in the products listed above. We are researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available.

Additional query words: comm 


Keywords          : kbenv win95 wincomm winnt wpp95 
Version           : 95
Platform          : WINDOWS 
Issue type        : kbprb

Last Reviewed: January 21, 1999