For XP Home, no. For XP Pro, press CTRL-ALT-DEL twice at the Welcome Screen, with no users logged in. Enter Administrator and the password for that account in the logon dialog that you'll see.
For XP Home, you need to login as Administrator in Safe Mode only. For XP Pro, press CTRL+ALT+DEL twice at the Welcome screen and you will see the classic logon box. Login as Administrator.