This article describes how to troubleshoot MS-DOS-based
program problems in Windows.
Test the Ntvdm Subsystem
The first thing to test when you are having problems with
MS-DOS-based programs is the Windows 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:
- Click the Start button, and then click Run.
- In the Open box, type command.com, and then click OK.
This should start a command prompt window. If this does not
work properly, there is a problem with the NTVDM subsystem and you should check
the following items:
- 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:
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 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
- 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:
- 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:
Ntvdm.dll (Windows NT 3.1 only)
- The registry entries associated with the NTVDM subsystem
The following functions do not work in Windows:
- 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.
This means that Windows does not support 16-bit programs that
require unrestricted access to hardware. If your program requires this, it will
not work in Windows NT or Windows 2000.
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:
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.
- 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.
- Right-click the desktop, point to New, and then click Shortcut.
- In the Command Line box, type the full path to the file you want to run, and then
- 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.
- Right-click the new shortcut, and then click Properties.
- On the Program tab, click Windows. This opens a dialog box for the path to the Autoexec and Config
- Type the full path to the files you created, and then
click OK in both dialog boxes.
There are other settings in a program's properties. If your
program is not working properly, you may want to check all the tabs and make
sure that the program settings are set to the manufacturer's specification. If
the program is still not working, the vendor of the program should be contacted
to see if the program is supported under Windows.
information, please see the following articles in the Microsoft Knowledge Base:
TITLE : MS-DOS Application I/O Operations Cause Floppy Drive Access
TITLE : NTVDM Error: There Is No Disk in the Drive
TITLE : Entries in CONFIG.NT or AUTOEXEC.NT May Cause NTVDM Errors
TITLE : Err: "Hidden Console of WOW VDM" Running 16-bit or DOS App
For additional information about printing in an MS-DOS-based
program, please see the following article in the Microsoft Knowledge Base:
TITLE : Troubleshooting Printing Problems in Windows