(NOTE: This is support information that was originally provided on Symantec's website.  The information is provided without warranty of any kind.  Use at your own risk.)

Knowledge Base

Errors regarding 16-bit MS-DOS subsystem

After installing Norton AntiVirus 2000 or 2001 under Windows NT/2000, you see error messages regarding corrupted 16-bit subsystems, such as the following:
- 16 bit MS-DOS Subsystem <path> <file name>. An installable Virtual Device Driver failed DLL initialization. Choose 'Close' to terminate the application. Choices are Close or Ignore.
- 16 bit MS-DOS Subsystem <path> SYSTEM\CurrentControlSet\Control\VirtualDeviceDrivers. VDD. Virtual Device Driver format in the registry is invalid. Choose 'Close' to terminate the application.
Choices are Close or Ignore.

In some cases, clicking Ignore enables the program to run correctly, but the error message continues to appear when 16-bit programs run.

This problem is being investigated. According to Microsoft technical support, these errors are linked to the following registry key:


This key has an VDD binary value that points to:


If the VDD binary value is removed, then the 16-bit subsystem returns to normal and is functional.

You must follow the instructions in both sections, and you must remove the VDD binary value first.

To remove the VDD binary value:

CAUTION: We strongly recommend that you back up the system registry before making any changes. Incorrect changes to the registry could result in permanent data loss or corrupted files. Please make sure you modify only the keys specified. See the document How to Back Up the Windows 95/98/NT Registry before proceeding

To update Symevent files:

Product(s): Norton AntiVirus 2000, Norton AntiVirus 2001, Norton AntiVirus 2002
Operating Systems(s): Windows NT 4.0, Windows 2000
Document ID: 2000030812224206
Date Created: 03/08/2000
Last Modified: 02/22/2002