Configure Windows XP to Automatically Login
After downloading fixes from Windows Updates page or via Automatic Updates, you may notice that Windows XP no longer logs into your account automatically. This is usually caused after the installation of .NET Framework from Microsoft. It creates an additional user account called ASP.NET, which you can see in the Control Panel User Accounts applet. But, you neither need to remove this update nor delete this account. You can still configure Windows XP to automatically login using these methods:
Click Start, Run and type CONTROL USERPASSWORDS2, and click Ok. Select the user account from the list (the account to which you want to automatically logon). Uncheck Users must enter a user name and password to use this computer option, and click Ok. Type the user account password and complete the process.
For Windows XP Home, don't try to auto-login as the built-in Administrator, as you'll receive an error message.
Method 2: Using TweakUI
Open TweakUI (Click Start, Programs, Powertoys for Windows XP). Expand the Logon branch, and click Autologon. Turn on the "Log on automatically at......" option, type your username and password, and click Ok.