Are you running WinXP SP2 or SP3?
Is Windows Live Mail installed?
What anti-virus application or security suite is installed and is your
subscription current? What anti-spyware applications (other than Defender)?
What third-party firewall (if any)?
Has a(another) Norton or McAfee application ever been installed on the
computer (e.g., a free-trial version that came preinstalled when you bought
it)?