到WINDOWS的命令行了（‘DOS’ 下），切换到你的MySQL bin目录下。 比如我的是 C:\Program Files\MySQL\MySQL Server 5.1\bin
然后敲下面的粗体的命令。注意你的my.ini位置。

C:\Program Files\MySQL\MySQL Server 5.1\bin>mysqld --defaults-file="C:\Program
Files\MySQL\MySQL Server 5.1\my.ini" --console --skip-grant-tables
090515 22:06:09 [Warning] The syntax '--log' is deprecated and will be removed i
n MySQL 7.0. Please use '--general_log'/'--general_log_file' instead.
090515 22:06:09 [Warning] The syntax '--log_slow_queries' is deprecated and will
 be removed in MySQL 7.0. Please use '--slow_query_log'/'--slow_query_log_file'
instead.
090515 22:06:09 [Warning] The syntax '--log' is deprecated and will be removed i
n MySQL 7.0. Please use '--general_log'/'--general_log_file' instead.
090515 22:06:09 [Warning] The syntax '--log_slow_queries' is deprecated and will
 be removed in MySQL 7.0. Please use '--slow_query_log'/'--slow_query_log_file'
instead.
090515 22:06:09 [ERROR] The update log is no longer supported by MySQL in versio
n 5.0 and above. It is replaced by the binary log. Now starting MySQL with --log
-bin='' instead.
090515 22:06:09 InnoDB: Started; log sequence number 0 324221
090515 22:06:09 [Note] mysqld: ready for connections.
Version: '5.1.33-community-log' socket: '' port: 3306 MySQL Community Server
(GPL)

看到这个结果就说明MySQL已经起来了。
再开一个DOS窗口，同样切到mysql bin目录下，
C:\Program Files\MySQL\MySQL Server 5.1\bin>mysql -uroot mysql
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 2
Server version: 5.1.33-community-log MySQL Community Server (GPL)

Type 'help;' or '\h' for help. Type '\c' to clear the buffer.

mysql>

mysql> UPDATE user SET Password=PASSWORD(’newpassword’) where USER=’root’;  
mysql> FLUSH PRIVILEGES;  
mysql> quit  

转自 。。。。。http://blog.163.com/dongjuan_1112/blog/static/546829832010981354045/