本人用的是dell笔记本，windows7专业版系统，开机时莫名其妙弹出一个窗口，内容如下：This computer system,is protected by a password authentication system.You can not access the data on this computer without the correct password.Please type the system or administrator password. 按F12 F8 DEL 都出来这个窗口，求救啊，怎么破译或删除？