First, let's be sure we are talking about the same thing. I'm not talking
about an account you created. There is a default account in both XP Home
and XP Pro, it is named "Administrator" and it is usually hidden, though,
until a user creates a user account, often it will appear on new systems, at
least until the first user account is created. Hence, this would be an
account you didn't create at the end of XP setup, rather its an account
automatically created during setup with the option of also password
protecting it.
You can always tell the difference between this and user created accounts as
it can only be named "Administrator," the name cannot be changed and it is
the only account by that name. NOTE: not the only account admin privileges,
just the only account with that name.
If in fact you are talking about this default account, you might try running
a search on the Internet for an application that helps find lost passwords.