Software

So basically I have my own personal account with Admin privileges and I recently changed it and being stupid forgot what it was after an absence from my computer.
I used a password reset disk but my account is locked so it couldn't change it and I tried logging on using the default Admin account on my XP yet it won't let me access it (I have all the correct details for the Admin account).
In order to get into my PC I managed to log onto a guest account made long ago (default guest also won't log in) and cannot do much with this account as it has no Admin rights.

Has anyone got a way of solving my troubles by either:
*Helping me change the password on my personal account.
*Helping me get the Admin account to be able to log in.
*Or giving my current guest account Admin rights.

Looking forward to hearing from you :)