|open up the desktop case and remove the bios battery from the motherboard (looks about the size of a nickle) for 30 seconds and then replace it. That should remove the bios password if there is one. (You will have to reset your clock, etc after that|
If it is the sign in password, try tapping f8 on startup and select safe mode. Then go into user accounts and delete that user.
If neither works, you will have to reformat and put in a new operating system
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