Prevent access to 16-bit applications

Specifies whether to prevent the MS-DOS subsystem (ntvdm. exe) from running on this computer. This setting affects the launching of 16-bit applications in the operating system. You can use this setting to turn off the MS-DOS subsystem which will reduce resource usage and prevent users from running 16-bit applications. To run any 16-bit application or any application with 16-bit components ntvdm. exe must be allowed to run. The MS-DOS subsystem starts when the first 16-bit application is launched. While the MS-DOS subsystem is running any subsequent 16-bit applications launch faster but overall resource usage on the system is increased. If the status is set to Enabled the MS-DOS subsystem is prevented from running which then prevents any 16-bit applications from running. In addition any 32-bit applications with 16-bit installers or other 16-bit components cannot run. If the status is set to Disabled the MS-DOS subsystem runs for all users on this computer. If the status is set to Not Configured the OS falls back on a local policy set by the registry DWORD value HKEY_LOCAL_MACHINE -> System -> CurrentControlSet -> Control -> WOW -> DisallowedPolicyDefault. If that value is non-0 this prevents all 16-bit applications from running. If that value is 0 16-bit applications are allowed to run. If that value is also not present on Windows 8. 1 and above the OS will launch the 16-bit application support control panel to allow an elevated administrator to make the decision; on windows 7 and downlevel the OS will allow 16-bit applications to run. Note: This setting appears in only Computer Configuration.

Additional Information

  1. Registry path is:

    HKEY_LOCAL_MACHINE -> Software -> Policies -> Microsoft -> Windows -> AppCompat # VDMDisallowed

  2. The Administrative Template path is:

    Windows Components -> Application Compatibility


* Making mistakes while changing registry values can affect your system adversely. We recommend you to create a System Restore point before making registry manipulation. If you're new to Registry Editor, read this beginner's guide.
** To locate the registry and administrative template path, checkout beginner's guide.
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