Administrator password

[Gair E. Bridges]

I can no longer log in to my account as administrator.
have tried every password I have ever used for anything
but to no avail. Have even tried to reinstall program
but won't let me do that since I don't have Admin.
authority. How do I get back on my computer?

 

[Longhorn]

Which edition of XP? If home then you can boot into safe mode with blank
password.