You can configure Windows XP to automate the logon process if your computer is not part of a domain. Computers configured in a business environment generally have a domain and for those machines the option "Users must enter a username" does not appear because a password must be given to access the local area network or domain.
1.Click Start, click Run, and type control userpasswords2.
2.Uncheck the "Users must enter a username and password to use this computer" check box.
4.Enter the user name and password you wish to automatically log on with, and then click OK.
5.Click OK again and you're all done.
This feature allows other users to start your computer and use the account that you establish to automatically log on. Enabling auto logon makes your computer more convenient to use, but can pose a security risk since anyone can just turn the machine on and access your files.