KB150420 - Err: Win16 Subsystem Unable to Enter Protected Mode

Article ID: 150420

Article Last Modified on 11/1/2006

Microsoft Windows NT Workstation 3.5
Microsoft Windows NT Workstation 3.51
Microsoft Windows NT Server 3.5
Microsoft Windows NT Server 3.51

This article was previously published under Q150420

SYMPTOMS

When you attempt to access a 16-bit application from Windows NT and are using Fprot.exe, the following error message is displayed:

The Win16 Subsystem was unable to enter Protected Mode, DOSX.EXE must be in your AUTOEXEC.NT and present in your PATH.

CAUSE

Fprot.exe inadvertently changes the file's attributes to read/hidden/system attributes. The following may be affected:

WINNTxx
WINNTxx\SYSTEM
WINNTxx\SYSTEM32
WINNTxx\SYSTEM32\DRIVERS
WINNTxx\SYSTEM32\REPAIR

RESOLUTION

Compare the damaged system with a fresh install of NT on a second computer and reset the attributes with either the "attrib" command or File Manager.

MORE INFORMATION

ATTRIB [+R | -R] [+A | -A ] [+S | -S] [+H | -H] [[drive:] [path] filename]
[/S]

+   Sets an attribute.
-   Clears an attribute.
R   Read-only file attribute.
A   Archive file attribute.
S   System file attribute.
H   Hidden file attribute.
/S  Processes files in all directories in the specified path.

Keywords: KB150420