How do you prevent your PC from breakdown due to viruses?

I have experienced many instances wherein my PC just would not start, would not respond or would not simply turn the screen black. It is indeed irritating and inconvenient that all my important files are constantly in danger. Some known antiviruses seem to be not helping since even though I have them installed, viruses could still damage my PC. In this time wherein computer viruses and worms can easily invade and corrupt personal computers, I would like to know the sure way to prevent these viruses from damaging my hardware.

