NTVDM Error Opening COM Port
Article ID#: KIN0043
When installing and configuring a RDP serial interface, you may encounter a
NTVDM hard error opening the COM port.
Change switch 422-3 to Yes from the System menu --> Switches --> in the search field enter 422-03 and change the Setting to
Yes. With switch 422-03, "Use Individual Folios A & B" set to Yes, group pay
codes are NOT stored in the C7 table. Exit out of RDPWin completely and log
If the problem continues to occur, see Solution 2.
Microsoft support recommends
checking the settings of the Windows virtual DOS machine subsystem. To
view these settings, perform the following commands:
- Open a command prompt.
- If you cannot open a command prompt, there is a problem with the NTVDM
subsystem. Check the following items:
- Check the Config.nt and Autoexec.nt files in the SystemRoot%\System32
folder for non-standard settings.
lh %SystemRoot%\System32\Nw16 (only if CSNW is installed)
lh %SystemRoot%\System32\Vwipxspx (only if CSNW is installed)
***REM any other lines in the Config.nt or Autoexec.nt. Note
that using REM statement in either of these two files to remark out
entries may cause other programs to not function correctly.
- If by changing the settings above the problem is not resolved, it may be
necessary to stop programs from running at startup. To determine if
any programs are running at startup, review the following locations:
- %SystemRoot%\Profiles\user_name\Start menu\Programs
- %SystemRoot%\Profiles\Default user\Start menu\Programs
- Examine the NTVDM system files in the %SystemRoot%\System32 folder for
correct version by checking the size and date:
- Ntvdm.dll (Windows NT 3.1 only)
- The registry entries that are associated with the NTVDM subsystem are:
This key stores the environment variables from the Config.sys and
Autoexec.bat files for use in Windows.
This key stores the device drivers that are used in an NTVDM
session. Windows Setup creates these entries when a device driver
The information contained in this article comes
directly from Microsoft knowledge base article # 314106.