The simplest way to not show unread email messages on the
Welcome screen is to download, install, and run TweakUI from
Microsoft. Once you've installed TweakUI, go to Start -> All
Programs -> Powertoys for Windows XP and launch the program.
Click the + sign next to Logon. Click on Unread Mail. Make the
appropriate changes in the right hand pane. Click OK. Restart
your compute to see if you get the desired results.