mysql安装位置:C:\Program Files\MySQL\MySQL Server 5.1\

一/打开cmd终端

输入:>net stop mysql

         >cd C:\Program Files\MySQL\MySQL Server 5.1\bin

         >mysqld --skip-grant-tables

二/打开另一个终端

         >cd C:\Program Files\MySQL\MySQL Server 5.1\bin

         mysql>mysql -u root

         mysql> use mysql
                    database changed
         mysql> update user set password=password("123456") where host="localhost" and user="root";                   ##新密码改为123456

         mysql> flush privileges;
         mysql> quit

三/重启系统,完成