MSDOS subsystem and Autoexec.nt / Config.nt

CONFIG.SYS and AUTOEXEC.BAT are files essential to DOS. They also exist in Windows NT but they are called CONFIG.NT and AUTOEXEC.NT and reside in C:\WINNT\SYSTEM32.

They are executed every time a DOS subsystem is created within NTVDM.EXE, which means every time you start a 16-bit program (Like Command.com). They will configure the environment in which the program will be executed in. This includes WinNT DOS drivers like ANSI.SYS.

Note if the AUTOEXEC.NT has been damaged/lost (usually deleted by a virus, so remember to update virus scanner), then one can usually restore the AUTOEXEC.NT by copying it from \Windows\Repair to \Windows\System32. When running a DOS program without the AUTOEXEC.NT being in place it will give the following error message:

16 bit Windows Subsystem - C:\Windows\System32\AUTOEXEC.NT. The system file is not suitable for running MS-DOS and Microsoft Windows applications. Choose 'Close' to terminate the application.

More Info MS KB324767

Note it possible for Windows NT4/2000 to parse the AUTOEXEC.BAT (Placed in the root of the system-drive) during user logon, and append the PATH environment variable to the user PATH. The parsing of the AUTOEXEC.BAT is controlled by this STRING registry value:

[HKEY_CURRENT_USER \Software \Microsoft \Windows NT \CurrentVersion \Winlogon]
ParseAutoexec = "0" (Default = "1", Ignore = "0")

More Info MS KB124551

More Info MS KB101875
More Info MS KB103656
More Info MS KB129128
More Info MS KB165214
More Info MS KB220155
More Info MS KB301911
More Info MS KB314106
More Info MS KB314495

Related Lock MSDOS subsystem to a single core to avoid crashes
Related Disable the MSDOS and Win16 subsystem

Updated: 21 January 2010

Comments:

  1. anonymous says:

    I'm trying to use some aliases for MS-DOS commands in Vista.
    I've edited C:\Windows\system32\config.nt adding this line: "doskey finder=findstr /I /M /R $*".
    It doesn't work: a new command prompt still says "finder" is unknown command. Why this? Where is my error?

    PS
    Even after a logoff-logon or reboot it's still the same.

  2. Snakefoot says:

    I didn't know people was still messing about in the MS DOS command prompt (command.com) and wasn't using the much better standard command prompt (cmd.exe).

    I have little experience with doskey, but it seems you could get the same thing to succeed by creating a batch-file called finder.

  3. Mike Miller says:

    To set it so the command is available from anywhere within the Command [CMD] prompt you need to set the path= command
    [i.e. path=C:\windows\;C:\ as well so when you type in finder it knows to not only associate the shortened name to the command but where to find the command you are reffering to as well. CMD [or command] is AWESOME for techs working in network environments [I.E. LOGON scripts!] most users with only one or 2 machines will wonder why we worry bout command prompt as you never really need it to modify singular accts that will never move or need to migrate changes to multiple machines

  4. Mike Miller says:

    multiple machines in a constant manner* [or if you have say a user that knows nothing and yet you need to set things up when they logon for them as they themselves do not know how to do so [or you dont want them to]]

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