|liloka do you know the administrator password?|
To access the administrator account, at the welcome screen do a couple of control alt deletes. This will bring up a logon box. Type in administrator and the password.
If you do not know the administrator password and you have no admin backup account made, you will need to reinstall XP thereby setting the administrator password to one you know.
This may not be a bad thing for you as it will clear out stuff you don't want or need anymore.