Hmm, the fourth leading cause of computer catastrophe is... Acts of God?"...my vicar's house was stuck by lighting and her PC has never worked again."

We were somewhat surprised about this, but maybe it's because of the climate in Toronto. Up here, thunderstorms are a pretty isolated event, reserved to maybe four months a year. Make no mistake though, lightning strikes do cause serious damage to electronic components, especially your computer, and especially the modem.

"It was a cloudy day, lightning flashed in the next county. Since I am near the county lines, my telephone lines go into that county. A electrical surge came... my modem caught fire."

Lightning strikes can cause huge electrical surges in the power and phone lines entering your house. Over longer distances this gets filtered out, but at close range it can be devastating.

"...yeah my XBOX, DSL modem, a network hub and every network adaptor in the house died when lightning hit the phone lines outside. This fried the modem then the hub and from the hub, all the NICs in the house including the one in my XBOX."

Often modems and other phone line devices are more vulnerable to this than other computer components that depend on the better-shielded power lines. Of course, if your modem is built into your motherboard, it's not looking good for you.

How Not to Kill Your Computer This Way

Remember when your mother used to tell you not to watch TV during a thunderstorm? She had it right (well mostly). You should not be using your computer if lightning is striking anywhere close to you, and for its safety, unplug the modem from the phone jack. Go watch TV instead, TVs are easier to replace. Actually, go outside and watch the thunderstorm; thunderstorms are cool.

If you are in an area that sees frequent lightning strikes, get a decent quality UPS (Uninterruptible Power Supply)that also monitors and conditions power and has a phone line/network cable surge protector. This will provide protection against sudden surges and other lightning-triggered electrical freakiness through the power, phone, or cable modem LAN.

The Bad Seed

"I tried powering up the system but it wouldn't. I tried tapping the switch a couple more times then a bright light appeared, followed by a bang and some smoke. Turns out the power leads on my $5 lazer LED accessory were switched."

This is kind of a catchall category, but it's an important one. One of the major killers of computers is the installation of parts that are inimical to the system, whether the parts themselves are faulty or just incompatible.

"One day I got an old HDD from my cousin and I installed it into my computer. It was fine when I booted into Windows but suddenly the screen showed nothing and I started to smell something burning... I quickly switched off my computer and removed the HDD and tried again but it didn't work. When I opened my case to try to figure out what's happening, the IC of the mainboard started to smoke..."

The Bad Seed. Sounds menacing and it is. Once a computer component (like memory or a video card) or peripheral goes bad, possibly due to damage caused by a power supply failure, it can continue to kill system after system like a virus as its hapless owner tries to figure out what is causing the problem.