How to recover Admin username and password on XP?

I have not used my WIN XP Admin username and password for a while, or I should say, I thought I was logging as Admin. untill I tried to download XP SP2. The OS will not allow me to download SP@. Does any one know how to recover the Admin username and passwords? Do I have to re-install Win XP?

home.eunet.no/~pnordahl/ntpasswd/


Have fun,

Thanks Sahirh, Actually I was logged in correctly as the Administrator in Win XP. I was not able to download SP2. I used one of the two free questions from Microsoft. They gave instruction. Thanks much for the link.