We never allowed personalization of of the desktop or the user to install programs on their computers. The fun part is that our two help desk people caught on quickly played along with it. This gag was reserved for the top producers and usually meant a paid company lunch and a bonus check while their computer was being "Wiped" Clean.
The gag usually took them through a series of questions about surfing porn sites, installing programs and everything else that wasn't alowd by corporate rules. After that they were usually asked to report to my office or their sales managers office just before lunch or quiting time. All along they thought they were going to mis their lunch hour and get poop for something they didn't do. It was always fun to see the look on their face and the way they acted while being questioned about something they didn't do. All was forgiven when they were praised, given a bonus and taken out for food.