MORE BACKGROUND: Haven't yet installed SP2; auto update attempt on Friday failed.
THE PROBLEM: This morning, the weekly Norton AV scan picked up the subject intruder. The Notification message, under "Action Taken" noted the following: 'Clean failed. Delete failed: Access denied'.
I located the file in C:Windows and tried to delete it directly. It failed noting the following: 'Access denied. Make sure disk is not full or write protected and file is not currently in use'.
I ran Pest Patrol, Spybot and Adaware to no avail.