I can't get my windows xp pword?

I have a dual boot with vista ultimate and windows xp sp2. whenever i try to boot with xp it takes me to the bios and asks me for the adminastrators p/w. I put my pword in for my user account but it says it's invalid i also tried 1 of my other typically used pwords. Can it be mixed up with the vista's account adminatator? but my vista account works fine. can any1 hlp me?