Registry Entries for NT Virtual DOS Machine (VDM):

SUMMARY

This article covers the registry entries for Windows NT virtual DOS machines (VDMs).

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet \Control\VirtualDeviceDrivers

This registry entry contains all the virtual device drivers (VDDs) that are loaded in the VDM at initialization. This is entry is mainly intended for independent hardware vendors (IHVs) who want to provide virtual device drivers with their native device drivers. By default, this entry does not have any VDDs.

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\WOW

This registry entry supports the following keys:

 - cmdline:     The command line which NT uses to create NT virtual
                DOS machines (VDMs) for MS-DOS-based applications.
                This entry is not useful for end users in any way.

 - size:        This tells NT what should be total memory size for
                the VDM created for MS-DOS-based applications. This
                includes conventional and extended memory. Default
                value is 0, which means NT should choose the size
                depending on the machine configuration. If this value
                is altered, NT uses it rather than determining a value
                itself.

 - wowcmdline:  Same as cmdline described above but used by Windows on
                Windows (WOW) VDMs.

 - wowsize:     same as size described above but used by WOW VDMs.

 - KnownDLLs:   This is only for WOW applications. If a DLL name is
                included in this entry and the application loads it
                without specifying the full path, the WOW subsystem
                loads that DLL from the Windows NT system directory
                (\SYSTEM32). This ensures the Windows NT loads a
                specific version of the WOW DLL rather than the
                application's version of that DLL (since the
                application's version of the DLL may not work under
                Windows NT.

 - LPT_Timeout: This is used by MS-DOS-based applications. There is no
                specific call to tell MS-DOS that the print job has
                completed. Under Windows NT (which spools print jobs),
                it is important to close the print job for printing to
                start. NT VDMs uses this timeout value to detect no
                printing activity before closing the print job handle.
                The default value is 15 seconds.