computer defective yet expensive?

What is this topic about? Actually , a friend of mine inform me of worm infestation for his computer and make his computer cannot log in. Yes, worm infestation for computer no more computer virus. Computer worm more bulky, more damage done, more difficulty to fix.
So for computer user like me always pray not to get worm for computer. If i got one in my computer , i will format my computer (i previously got one). After the worm, I kind of got Obsessive compulsive disorder and backup my data at weekly basis.any worm attack means one weeks work gone. Always two backup(one in portable hard disk, another either in thumb drive or dvd).
in conclusion, computer is an expensive item but defective because it is vulnerable to worm,virus attack. just like us , easy to get disease if we are not keeping well.