Disabling the MSDOS and WOWEXEC Subsystems on Terminal Server

ID: Q220159

The information in this article applies to:
  • Microsoft Windows NT Server version 4.0, Terminal Server Edition
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.

SUMMARY

Performance issues may occur on a Terminal Server computer running 16-bit or MS-DOS programs. Because multiple users can start sessions on a Terminal Server computer at the same time, it is possible that the System Administrator may not be aware of 16-bit programs or MS-DOS programs running at the same time. The System Administrator can disable the NTVDM and WOWEXEC subsystems, which keep the programs from running, as well as generate an error message that identifies the programs.

NOTE: If logon scripts are used, please change the file extension from *.BAT to *. CMD. This allows the scripts to run without starting the NTVDM subsystem.


MORE INFORMATION

You can disable only the 16-bit Windows On Windows subsystem, or both the Windows On Windows and the Windows NT Virtual DOS Machine (NTVDM) subsystems, however, you cannot disable just the Windows On Windows subsystem by modifying the registry.

To modify the 16-bit Windows On Windows subsystem:

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. If you are running Windows NT, you should also update your Emergency Repair Disk (ERD).

  1. Start Registry Editor (Regedt32.exe).


  2. Locate the CMDLINE (for MS-DOS applications) and WOWCMDLINE (for 16-bit Windows applications) values under the following key in the registry:


    3. HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\WOW
  3. Adding a character to the beginning of the string will keep the subsystem from running, but it will keep the old value in tact to easily revert back to the old setting.


  4. Quit Registry Editor. These registry changes are dynamic and it is not necessary to restart.


Keep Task Manager running to help determine the current state of the system. If an NTVDM is running, you may wish to stop the NTVDM process currently running to ensure that the registry changes are reflected when creating a new NTVDM.

This keeps 16-bit and MS-DOS programs from running. Also, an error message may be displayed giving file and path information for the program you are trying to run. The following are examples of the messages that are displayed:
MSDOS:
Windows cannot find edit.com
This program is needed for opening files of type "MS-DOS application"

Windows:
Cannot find d:\WTSRV\system32\sysedit32.exe. Windows needs this file to run d:\WTSRV\system32\sysedit32.exe.

Additional query words: Phrase: cannot find

Keywords :
Version : winnt:4.0
Platform : winnt
Issue type : kbinfo


Last Reviewed: January 10, 2000
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