1. Management tool---Service inside stop MySQL service.
2. Control Panel---Uninstall MySQL, delete C:\Program files\mysql directory.
3. This is the most critical step, only to do the first two steps, the password or can not be modified, because MySQL also has files, that is, in C:\Documents and Settings\All Users\Application Data inside the MySQL folder, This file is not cleared and is the source of the old password for MySQL reload. Then delete the MySQL folder.
4. Check if there is a My.ini file in the C:\WINDOWS directory and delete it
5. Heky_local_machine,software,mysql deletion in the registration table
Hkey_local_machine\system\controlset001\services\eventlog\application\mysql Directory Removal
Hkey_local_machine\system\controlset002\services\eventlog\application\mysql Directory Removal
Hkey_local_machine\system\currentcontrolset\services\eventlog\application\mysql Directory Removal
MySQL Complete removal tutorial