My mother had a rough case at work. She has two comp. One is connected to the net, the other is not. Here one day she makes a chat on the main comp (because it is not connected to the net), turns to the second comp, he writes that he found a Trojan. My mother removed him. However, as their system manager said, the Trojan left traces in view of the desktop image with the inscription "Spy detected! Update antivirus program on your computer". Mom was scared at first, but then saw that all the badges were in place and calmed down. So this crazy Trojan left another message. 10 minutes later, the computer issued a blue screen of death. Ma called the system manager, he jumped, began to write out the error numbers, and at some point hit the hand of the mouse... And what do you think? The blue screen of death turned out to be the usual screensaver, which turns on after some time of non-use of the comp.
Mom says their system maker 5 minutes pumped out after that.