I found this in a few different places around the 'net - hopefully it's helpful:
Automatically Log On a User Account in Windows XP
This article describes how to automatically log on a user account during the Windows startup process.
Note: This process only works if the computer is not joined to a domain.
Requirements
- The Welcome screen must be available.
- Guest account access must be turned off.
- There must be only one user account on the computer.
- The user account must not have a password.
Make the Welcome Screen Available To make the Welcome screen available:
- Click Start > Control Panel > User Accounts.
- Click Change the way users log on or off.
- Click to select the Use the Welcome screen for fast and easy logon check box.
- Click OK.
Turn Off Guest Account Access To turn off Guest account access:
- Click Start > Control Panel > User Accounts.
- Click the Guest account.
- Click Turn off Guest access.
Remove the Password from a User Account To remove the password from a user account:
- Click Start > Control Panel > User Accounts.
- Click the user account.
- Click Remove my password.
- Type the password in the Type your current password box, and then click Remove Password.