Register a new account, enter a password of your choice.
Then log into phpmyadmin, on the left navigate to your VB database, and users table.
Click on "browse" from the top navigation and find that new account you just registered from the list.
Copy the encrypted data from the password field.
Then find your main admin account(userid should be 1).
Click edit and find the password field.
Paste the encrypted data you copied from the other field into this one.
Then go back and copy the data from the SALT field of the new account into the admin account.
Then proceed to login with the main admin account and the new password you just created.