Jerry wrote:
  I know that.  I have a copy of Ralf Brown's
Interrupt List
 <http://www.ctyme.com/rbrown.htm> for the x86 platform. I also know
 there are some DOS specific structures that I have to duplicate for
 compatibility.  My problem is that I need to know how to program a NT
 System Service.
 
NTVDM/VDM is nor a service nor a subsytem. The only "hack" for it is in
CreateProcess which launches ntvdm.exe with the application name
suffixed (this code is already in trunk).
The rest depends on:
1) ABIOS implementation in ntoskrnl
2) GUI calls in Win32K
3) NTVDM
4) VDM support in CSRSS
5) BIOS, io.sys, config.sys, etc files
Best regards,
Alex Ionescu