Int 21 Fn 2B  - Desqview - Installation Check                              [Q]

   AH = 2Bh
   CX = 4445h ('DE')
   DX = 5351h ('SQ')
   AL = subfunction (DV v2.00+)
       01h get version

       Return: BX = version (BH = major, BL = minor)

       Note: early copies of v2.00 return 0002h
       02h get shadow buffer info, and start shadowing

       Return: BH = rows in shadow buffer
           BL = columns in shadow buffer
           DX = segment of shadow buffer
       04h get shadow buffer info

       Return: BH = rows in shadow buffer
           BL = columns in shadow buffer
           DX = segment of shadow buffer
       05h stop shadowing

Return: AL = FFh if DESQview not installed

Notes: in DESQview v1.x, there were no subfunctions; this call only identified
     whether or not DESQview was loaded.  DESQview v2.52 performs function
     01h for all subfunction requests 0Ch and higher and appears to ignore
     all lower-numbered functions not listed here.
   DESQview versions 2.5x are part of DESQview/X v1.0x.
BUG:   subfunction 05h does not appear to work correctly in DESQview 2.52

See Also: INT 10/AH=FEh,INT 10/AH=FFh,INT 15/AX=1024h,INT 15/AX=DE30h