There was a smart arse in 1997 that wrote a virus that messed up a hardrive dont have a clue how it was done the source was never released, but he dropped in a timer and all infected systems were hit on the same day, thanfully tho the anti virus community got hold of it before d-day and most people were saved the pain.
This virus was called Chernobyl... My friend had it and ended up bying a new computer. There are some disasms of the virus available because I had it in one of the books about virused I used to have. You couldn't compile it but it showed some algorythms used.