You can configure Windows XP to automate the logon process if your computer is not part of a domain.
Click Start, click Run, and type control userpasswords2.
Clear the Users must enter a username and password to use this computer check box.
Enter the user name and password you wish to automatically log on with, and then click OK.
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.