CIH.exe
The CIH virus was unleashed in 1998, and set to activate a year later. It was spread on driver CD's and different websites, and even on a batch of IBM Aptiva computers. This was just a few months before the virus would activate.
This virus was probably one of the most destructive virii out there; not only did it overwrite the first 1024 kb of the harddrive thus overwriting the MBR and the FAT, but it also attempted to flash the BIOS. As BIOS restoration was not implemented at this time, the FlashBIOS chip itself had to be replaced in order to restore the computer to a working state.