Clane,
You have a few options available to you;
First of all I would try the simplest route. There is an Administrator account that is created with every windows Xp install. At the login screen, hit alt+ctrl+del 2 times, it should give you another login box, it may have a user name already inside it. Delete the user name, and type, "Administrator" no quotes. Hit enter, and it should log you in with admin privileges. From there goto Control Panel > User Accounts and change the passwords to your liking.
Second you can use the F8 key during windows startup. Continually hit F8 when your computer first turns on, BEFORE the windows screen loads. It will prompt you with choices on how to boot windows. Choose Safe Mode, and goto Control Panel > User Accounts and change the passwords there.
Good luck!