Troubleshooting MS-DOS-Based Programs in Windows NT 4.0

• Microsoft Windows NT Server version 4.0
• Microsoft Windows NT Workstation version 4.0

SUMMARY

This article describes how to troubleshoot MS-DOS-based program problems in Windows NT 4.0.

MORE INFORMATION

Test the Ntvdm Subsystem

The first thing to test when you are having problems with MS-DOS-based programs is the Windows NT Virtual Dos Machine (NTVDM) subsystem. You can use Command.com to test whether the NTVDM subsystem is running properly. You can start Command.com by performing the following steps:

1. Click the Start button, and then click Run.

2. In the Open box, type "command.com" (without quotation marks) and then click OK

• Check the Config.nt and Autoexec.nt files in the %systemroot%\system32 folder for non-standard settings.

  Using a REM statement, remark out all entries *except* the following default entries:

        Config.nt
        ---------
        dos=high, umb
        device=%SystemRoot%\system32\himem.sys
        files=20
  

        Autoexec.nt
        -----------
  

        lh %SystemRoot%\system32\mscdexnt.exe
        lh %SystemRoot%\system32\redir
        lh %SystemRoot%\system32\dosx
        lh %SystemRoot%\system32\nw16 (only if CSNW is installed)
        lh %SystemRoot%\system32\vwipxspx (only if CSNW is installed)
  

  NOTE: Another way to accomplish this is to expand Autoexec.nt_ and Config.nt_ from the Windows NT CD-ROM disc to the %SystemRoot%\SYSTEM32 folder.

• Close all other running programs. This can be accomplished by running Task Manager, closing all running programs, and making sure that there are no other NTVDM processes running. To start Task Manager, press CTRL+SHIFT+ESC.
• Prevent all programs from running at startup. Programs can run from three places at startup: the Startup groups, the Run and Runonce lines in the registry, and the "run=" and "load=" lines in the Win.ini file. You can check these places as follows:

      - The Startup groups are folders on the local hard disk located in
        the %SystemRoot%\profiles\%username%\start menu\programs and
        %systemroot%\profiles\default user\start menu\programs folders.
  

      - The Run and Runonce lines can be found in the registry under the
        HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\ key.
  

      - You can edit the Win.ini file using Notepad. It is in the
        %SystemRoot% folder.
  

• Verify the NTVDM system files in the %SystemRoot%\System32 folder. Check the following files and make sure they are the correct version by checking the size and date:

        Ntio.sys
        Ntdos.sys
        Ntvdm.exe
        Ntvdm.dll (Windows NT 3.1 only)
        Redir.exe
  

• The registry entries associated with the NTVDM subsystem are:

       HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Session
       Manager\Environment. This key stores the environment variables from
       the Config.sys and Autoexec.bat files for use in Windows NT.
  

       HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\
       VirtualDeviceDrivers. This key stores the device drivers to be used
       in a NTVDM session. These entries are created by Windows NT
       Setup when a device driver is installed.
  

Program-Specific Issues

The following functions do not work in Windows NT:

• All MS-DOS functions except task-switching APIs (program programming interface functions) are supported.
• Block mode device drivers are not supported. (Block devices are not supported, so MS-DOS IOCTL APIs that deal with block devices and SETDPB functions are not supported.)
• Interrupt 10 function 1A returns 0; all other functions are passed to read-only memory (ROM).
• Interrupt 13 calls that deal with prohibited disk access are not supported.
• Interrupt 18 (ROM BASIC) generates a message that says ROM BASIC is not supported.
• Interrupt 19 will not reboot the computer, but will cleanly terminate the current virtual DOS machine (VDM).
• Interrupt 2F dealing with the DOSKEY program call outs (AX = 4800) is not supported.
• Microsoft CD-ROM Extensions (MSCDEX) functions 2, 3, 4, 5, 8, E, and F are not supported.
• The 16-bit Windows subsystem on an x86 computer supports enhanced mode programs; it does not, however, support 16-bit VxDs (virtual device drivers). The subsystem on a non-x86 computer emulates the Intel 40486 instruction set, which lets the computer run Enhanced-mode programs, such as Microsoft Visual Basic, on RISC computers.

You should next check to see if the Autoexec.nt and Config.nt file settings are correct. Always try the default settings listed above. Some programs require special settings or drivers to run in the Config.sys or Autoexec.bat file. If this is the case, there are two options for initializing these files when starting your program:

• Enter these lines in the Config.nt and Autoexec.nt files in the %SystemRoot%\System32 folder.
• Create new Config and Autoexec files to be run when starting this program. To do so, follow these steps:

  1. Create the files and save them with the extension .nt in a folder

        other than %SystemRoot%\System32 (these files are usually saved in
        the same folder as the program.
  

  2. Use the right mouse button to click the desktop, point to New, and

        then click Shortcut.
  

  3. In the Command Line box, type the full path to the file you want to

        run, and then click Next.
  

  4. In the "Select a name for the shortcut" box, type the name for the

        shortcut, and then click Finish. This creates a new shortcut on the
        desktop.
  

  5. Use the right mouse button to click the new shortcut, and then click

        Properties.
  

  6. On the Program tab, click Windows NT. This opens a dialog box for

        the path to the Autoexec and Config files.
  

  7. Type the full path to the files you created, and then click OK in

        both dialog boxes.
  

  Every time this icon is started, it runs the Autoexec and Config files specified for the program. These settings are subject to the same restrictions as listed for MS-DOS-based programs.

For additional information, please see the following articles in the Microsoft Knowledge Base:

   ARTICLE-ID: Q171940
   TITLE     : MS-DOS Application I/O Operations Cause Floppy Drive Access

   ARTICLE-ID: Q102418
   TITLE     : NTVDM Error: There Is No Disk in the Drive

   ARTICLE-ID: Q156687
   TITLE     : Entries in CONFIG.NT or AUTOEXEC.NT May Cause NTVDM Errors

   ARTICLE-ID: Q142026
   TITLE     : Err: "Hidden Console of WOW VDM" Running 16-bit or DOS App

   ARTICLE-ID: Q163551
   TITLE     : Troubleshooting Printing Problems in Windows NT 4.0