INT 16 U - PCIBM PC Tools v5.1-8.0 DESKTOP - CHECK WHETHER DESKTOP LOADED RESIDENT
AX = FFC5h
Return: BL = Desktop state
00h if nonresident
nonzero if loaded resident
Note: available only when popped up; should call AX=FFEFh first to ensure
that DESKTOP is active
SeeAlso: AX=FFEFh,AX=FFF3h