"However, a police computer expert at Lundy's trial in 2002 said there was evidence that the file registry in the computer was disordered which suggested the time on the machine was tampered with.
Maarten Kleintjes demonstrated to the jury how it was possible to tamper with the computer and manipulate the 'shut down' time on the clock that was undetectable - giving Lundy an alibi.
He also said it was "far-fetched" that a computer virus could disorder the registry files.
He did not know of such a virus, and found no sign of a virus on the Lundy computer." Link1
"But a computer expert hired for the Privy Council appeal said there were several ways files could become disordered, including a virus.
Forensic examiner Michael Chappell discovered that the virus-checking program on the Lundy computer was out of date and it was infected with a virus known as a KAK worm. He traced it back to an infected email six weeks before the killings in August 2000 and when he deleted the virus, the registry files returned to their correct order." Link2
I am not sure but I think that the registry files and the time of shut down are two relatively separate issues. I don't know the significance of the registry files, but I think it is interesting how different the two viewpoints above are.