Оформил: DeeCo
Автор: http://www.swissdelphicenter.ch

type
   TKeyType = (ktCapsLock, ktNumLock, ktScrollLock);

 procedure SetLedState(KeyCode: TKeyType; bOn: Boolean);
 var
   KBState: TKeyboardState;
   Code: Byte;
 begin
   case KeyCode of
     ktScrollLock: Code := VK_SCROLL;
     ktCapsLock: Code := VK_CAPITAL;
     ktNumLock: Code := VK_NUMLOCK;
   end;
   GetKeyboardState(KBState);
   if (Win32Platform = VER_PLATFORM_WIN32_NT) then
   begin
     if Boolean(KBState[Code]) <> bOn then
     begin
       keybd_event(Code,
                   MapVirtualKey(Code, 0),
                   KEYEVENTF_EXTENDEDKEY,
                   0);

       keybd_event(Code,
                   MapVirtualKey(Code, 0),
                   KEYEVENTF_EXTENDEDKEY or KEYEVENTF_KEYUP,
                   0);
     end;
   end
   else
   begin
     KBState[Code] := Ord(bOn);
     SetKeyboardState(KBState);
   end;
 end;

 // Example Call: 
// Beispielaufruf: 

procedure TForm1.Button1Click(Sender: TObject);
 begin
   SetLedState(ktCapsLock, True);  // CapsLock on 
  SetLedState(ktNumLock, True);  // NumLock on 
  SetLedState(ktScrollLock, True);  // ScrollLock on 
end;