I'm pasting this from my web site:
To bypass the Welcome Screen and just have XP boot to your desktop, you can
only have ONE user account and have the Guest Account turned off.
Go to Control Panel, User Accounts. Click on Guest Account (if it's on),
then click on the button to Turn Off
If you have any other accounts that you did NOT create (like ASP.NET, then
you can delete that account as well. It may have been put there from a
previous Windows Update.
If you want to keep the other accounts and still have YOUR account
automatically log on, get Tweak from the MS PowerToys (freeware from
Microsoft)
Get it from Microsoft at:
http://www.microsoft.com/windowsxp/downloads/powertoys/xppowertoys.mspx
And get TweakUI
When it's installed, open it and double-click on the Logon item to open it
and then click on Autologon. Check the box titled Log on automatically at
system startup, enter your user name and password, and click on OK.
Now TweakUI will log you on using your user name and password even if more
than one account exists.
Tracy