reset mac login password

You'd have to boot up from the Recovery Partition, I think, though it should be possible from within the OS. Are you talking about an administrator password, the main one, or a secondary account, say, for a guest. If it's the latter, then go to system preferences, then Accounts, click on the administrator, type in your main name and password, then click on the account you want to change the password for.

If it's the former (the 1st one), reboot, hold down command (apple)+R to boot from the Recovery Partition, move the mouse to the top center of the screen, until you see OS X Tools, go to Terminal and open it. in the screen you see there, type in

"resetpassword" without the quotes, then press the Return key on the keyboard. This should get you into the main password reset app. from there you can reset the admin name and password,

john b