Hello, all!
My system : win2k, mysql4.0.17,php4.3.2

According to mysql manual, user is recommended to delete anonymous user having full privileges like,

mysql> DELETE FROM user WHERE Host='localhost' AND User='';
mysql> FLUSH PRIVILEGES;
mysql> QUIT
D:\mysql\bin>mysqladmin -u root password SECRET;
D:\mysql\bin>mysql -uroot -pSECRET mysql;

After this, I cannot access to root@localhost and had to reinstall.

Could you please explain what I was wrong and what to to?

Thank you in advance.

You need to flush the privileges tables

hehehe...
As I mentioned above, I did it right after delete command.
Several time I did. If I delete only anonymous, result is same.