I have been following these instructions for resetting root password for local installation of MySQL 5.6 on Windows 7 laptop.
I stopped
Updating this answer regarding to changes at MySQL 5.7:
0) shut down service mysql57
1) go to C:\ProgramData\MySQL\MySQL Server 5.7, note that ProgramData is a hidden folder
2) looking for file my.ini, open it and add one line skip-grant-tables below [mysqld],save
[mysqld]
skip-grant-tables
3) start service mysql57
4) by right, you can access the database, run mysql
5) and use the query below to update the password
update mysql.user set authentication_string=password('NEW_PASSWORD') where user='root';
6) shut down the service again, remove the line skip-grant-tables save it, and start the service again. try to use the password you set to login.