if you're talking about windows 7 log on password, there are two simple ways.
1. click the start button, type "change password" in the search box, select "change your password" from the search results. click open the change password window, enter the old password, then the new password, re-type the new password to confirm, click "change password button, and you're done. you can also create a hint so that you can remember the password from the hint. just don't make the password too simple to figure out or too complicated to remember. same goes for the password hint.
2. go to the control panel, then "Control Panel\All Control Panel Items\User Accounts\Change Your Password" (without the quotation marks), then click open the change pass window, then the rest is same as above.
edit: however, if you're locked out of a pc and you're asking for a password change, we cannot help you. the above procedure is only for a pc you own and want to change the password. we cannot help you with any kind of password protection bypassing. it is against thg forum rules.