Disable Mouse and Keyboard from Delphi Code

The BlockInput API function blocks keyboard and mouse input events from reaching applications.

Place a Button (name: "Button1") on a form (name: "Form1") and use this code for the button's OnClick event handler. Once you click the button your mouse and keyboard will be blocked for 5 seconds.
 

Note: BlockInput is available only on Windows 98 and newer, this is why we have a "FuncAvaial" procedure - to test the existance of a function inside a DLL. 
 

procedure TForm1.Button1Click(Sender: TObject) ;

 function FuncAvail(dllName, funcName: string; var p: pointer): boolean;
 var
   lib: THandle;
 begin
   result := false;
   p := nil;
   if LoadLibrary(PChar(dllName)) = 0 then exit;
   lib := GetModuleHandle(PChar(dllName)) ;
   if lib <> 0 then
   begin
    p := GetProcAddress(lib, PChar(funcName)) ;
    if p <> nil then Result := true;
   end;
 end;

 var
   BlockInput : function(Block: BOOL): BOOL; stdcall;

 begin
  if FuncAvail('USER32.DLL', 'BlockInput', @BlockInput) then
  begin
   ShowMessage('Your Mouse and Keyboard will be blocked for 5 seconds!') ;
   BlockInput(true) ;
   Sleep(5000) ;
   BlockInput(false) ;
  end;
 end;

end.