When the Commonwealth of Massachusetts issued Michael Fiola a Dell Latitude in November 2006, it set off a chain of events that would cost him his job, his friends and about a year of his life, as he fought criminal charges that he had downloaded child pornography onto the laptop. Last week, prosecutors dropped their year-old case after a state investigation of his computer determined there was insufficient evidence to prove he had downloaded the files.

An initial state investigation had come to the opposite conclusion, and authorities took a second look at Fiola's case only after he hired a forensic investigator to look at his laptop. What she found was scary, given the gravity of the charges against him: The Microsoft SMS (Systems Management Server) software used to keep his laptop up to date was not functional. Neither was its antivirus protection. And the laptop was crawling with malicious programs that were most likely responsible for the files on his PC.