To enter Windows XP Safe Mode, you must log on with an administrator account or an account that has administrator permissions.
On the PC displayed above, both my personal account, Tim, and the built-in administrator account, Administrator, have administrator privileges so either one could be used to enter Safe Mode.
Note: If you're not sure if any of your personal accounts have administrator privileges, choose the Administrator account by clicking on it and then providing the password.
Important: Not sure what the password is to the Administrator account? See How to Retrieve the Administrator Password in Windows XP for more information.