function BlockInput(fBlockInput: Boolean): DWORD; stdcall;external 'user32.dll';//delphitop.com

//点击按钮，系统会禁止一切输入操作，5秒后解除锁定。

procedure TForm2.Button1Click(Sender: TObject);

begin

  BlockInput(True);

  Label1.Caption := 'Blocked';

  Application.ProcessMessages;

  Sleep(5000);

  BlockInput(False);

  Label1.Caption := 'Unblocked';

end;