Power password on compaq persario 5000 series XP

Hello
Does anyone know how to get pass the password thats set when computer powers on ? I Madea password a couple of days ago ,and lost my paper I wrote it on ,and for some reason when I begin to typenothing happens it doesn't type my doesn't do anything.? so my only optionis is to restore it to original State.Ihave no install disk bought it off craigslist ,I would appreciate anysuggestions thanks