janism

Can anyone help? I inherited a PC recently and I have bought XP home to install on it. I want to do a clean install so I went into set-up to change the PC to boot from the CD drive but it is asking for a password. The person who gave me the PC doesn't know this password. Is there way around this? Also initially I just ran the CD and tried to install it over the OS that was there. This means that I have used my product key. Do I need to contact Microsoft in order to re-install using the same product key? Thanks for any help provided.