I once had a user who complained that her computer was infected with a virus. After investigating the incident, I determined that the virus had come from a USB thumb drive which the user had connected in order to retrieve some documents. I explained that I would have to wipe the computer and reinstall the OS. The next day, I returned a newly imaged pc to her and told her that she was good to go back to work. Less than fifteen minutes later, the user called me in total frustration, saying that the virus had returned. I went to the user's desk and informed her that there was no way the virus could have returned since it was a brand new computer. After questioning her, she informed me that she had plugged in the same USB thumb drive again in an attempt to retrieve her documents. I explained to her that she couldn't do that since that was the source of the virus. Her reply? "But I only plugged it in for a second!"