Of late, I have had several system failures. Trying to work out what has failed can be quite hard, potentially expensive and very aggravating. This is intended, not as a categorical description of failure modes, but as a sort of Cliff Notes to the way computers can fail. Enjoy! Hah!

RAM. Memory failures are nasty things. Computers don't even have to stop when these occur, but here are some things to look out for:

• If this is a new computer, and it starts to fail to boot, or starts up but quickly falls over - think failed Memory
• If the system is old and has been kept in probably too warm a location, and suddenly it stops, and rebooting only keeps it alive for short while - think failed Memory
• If the system freezes, lights on, but nobody home, sort of thing - think failed Memory

Power Supply Unit (PSU). These are boxes inside the computer that convert your mains power to the little volts that the motherboard and other devices need. They can be quite complex devices, and are designed to have multiple output voltages. Some have what are referred to as multiple busses, or bars, for a particular voltage. When a PSU fails, it is rarely smoke and flame out the back of the computer (though that has happened), it is often more pernicious.

• The system locks up, then just dies completely, frequently after the system has been up a long time - think failed PSU
• The system starts but then switches itself off. It can be restarted, but it doesn't last long - think failed PSU
• You switch it off, switch it on, and nothing happens, no fans, no LED's, no nothing - think failed PSU
• You left it running but now it's off, and it won't turn on - think failed PSU
• You see smoke come out the back when you switch on, the lights flicker, then there is no more activity - think failed PSU!

Another area of failure fun, is the hard drive (HD) giving up the ghost. Hard drives carry all you computers vital information, and the programs needed to start your computer. They fail. Always inconveniently. It may be a failing hard drive if:

• You hear a quiet 'ting' noise, like two small metal bits being bashed together - think failing HD
• Your programs experience crashes but the computer as a whole remains alive - think failing HD
• The computer powers up, the LED's come on, but that whine from the box does not occur and it doesn't start - think failed HD
• The computer boots up, but not every time. It gets recalcitrant! - think failing HD

There are many ways for a computer to stop working. These are very few of them, but they are the cheapest to fix (generally). Good backups can help, and keeping an eye on your hard drives health can save you many hours of pain. Remember, when Mother Nature wants to take back what she gave to us, she will, and in no uncertain terms.

Always bear in mind that you should never open a computer box while it is plugged in. When it has failed there could be short circuits and all manner of fried components under the hood.