How to erease a log on password

On what? And why? When you change it the old one automatically is changed.

If you want to start up without password. Then log in using your password. Go to control panel - users and then confirm your passord and do not enter a new one. That should reset the password to null. When you start it up again it shouldn't ask for a password to boot up.

Is it a BIOS password? i.e. does it appear even before Windows boots?

If you want to start up without password. Then log in using your password. Go to control panel - users and then confirm your passord and do not enter a new one. That should reset the password to null. When you start it up again it shouldnt ask for a password to boot up.

It will still ask for you to log in, just you won't have to enter a password.

If you go to the run dialogue and type in "control userpasswords2" and hit enter, you are given the option to have the computer skip the logon screen. You can enter the password and user to logon with or just choose a user account with a null password...

OP does need a more detailed question.