We all know that virus, it was very infamous of that time in 1999. Wrecked thousands of computers too. The "wrecked" part is because it overwrites a part of the BIOS in the system (with some unrelated content) and renders the system unbootable. Here is the page explaining about the dangers of that virus: CIH virus facts Not only it writes to BIOS unneccessarily, but it busts the boot sector as well! Come to think about that, the author of the virus might have known some registers which allows reprogramming of the BIOS chip. I have suspected he must have some access to a chipset datasheet during that time. From what I've read, if the virus has overwritten some parts of the BIOS, some of the computers *would* still boot - there will be no display unless you put an old ISA graphics card inside (I tried that before many years back), and you will see something like an "Award BootBlock, BIOS ROM checksum error" asking you for a floppy containing the correct *.BIN file. If you don't have the card, you could still know that it asks for a floppy - the floppy drive LED lit up and make seeking sounds. If it doesn't boot - I don't think it's worrying either. It's not the entire motherboard is busted. The BIOS ROM has the program gone wrong, so it doesn't boot, that's all. In that case, in modern times, you can get the EEPROM programmer from the eBay: EPROM EEPROM Programmer Pic BIOS Chip PCB 5c | eBay and just reprogram it with the correct BIOS. The programmer is expensive, but you can use it again for other brands of EEPROM. If you are too lazy to buy one, you can whip up your own programmer, probably with an Arduino or something. Oh, and the virus only attacked PCs with Windows 98. Newer PCs aren't affected at all due to the much better protection system nowadays.