How to Reset Administrator's Password

How to reset Administrators Password from "outside"

I go away for three months, my computer is unplugged from the wall as protection against lightning strikes etc. Before I shut it down, as added protection against unauthorised use, I set the Administrators Password, open and close the computer a few times - all works well - the Password was the Olympic Games date 080808 - when I returned this week, the password will not open my side of the computer - it also took a couple of goes before it got up and running, which, I suppose suggests the CMOS battery is about worn out - how can I reset the Administrators Password back to blank, which was the original state when the XP was originally installed?

One suggestion I have received is to use my original XP cd to "repair" the system and at some crucial stage reset the password.

Would this work? What is this crucial stage?

Is there a better way?