Int 16 Fn FEF1  U - Pc Tools V7 Only Cpsched/desktop - Alternate Installa  [U]

   AX = FEF1h
   BX = ???

Return: CX = 5555h if PC Tools scheduler (CPSCHED or DESKTOP) installed
   DX = 5555h

Note:  this function is identical to AX=FFD3h, and is implemented by the same
     code in DESKTOP

See Also: AX=FFF1h