Int 2F Fn DE00  - Desqview V2.26+ External Device Interface - Installatio  [Q]

   AX = DE00h
   BX = 4456h ("DV")
   CX = 5844h ("XD")
   DX = 4931h ("I1")

Return: AL = FFh if installed (even if other registers do not match)
   if BX,CX, and DX were as specified on entry,
       BX = 4845h ("HE")
       CX = 5245h ("RE")
       DX = 4456h ("DV")

Notes: AH=DEh is the default XDI multiplex number, but may range from C0h-FFh
   programs should check for XDI starting at DEh to FFh, then C0h to DDh
   the XDI handler should not issue any DOS or BIOS calls, nor should it
     issue DESQview API calls other than those allowed from hardware ints

See Also: AX=DE02h,INT 15/AX=5400h