The first item on the list is the source of power, the electricity.  Every computer system has to be plugged into some sort of power protection.  There are different levels of protection depending on what you need.  If you want to protect the equipment from damage then you need a surge protector.  If you need to make sure that the system continues to run in case of loss of power then you will need a UPS or Uninterruptible Power Supply. 

A surge suppressor is going to be the choice for most of the computers that we deal with.  Make sure that the suppressor you choose is UL listed and has a plug for your phone line from the wall and to the modem.  The modem is usually the first item that we forget about when it comes to surges.  We tend to forget that there is low voltage running through the phone lines and neglect to protect the modem.  Most of the new surge suppressors on the market now come with a manufactures warranty to protect the equipment that is plugged into it from damage due to electrical spikes and surges.  A good suppressor will cost about $35 and is available at most any store that sells computer supplies. 

If you have a system that needs to be on 24 hours a day, 7 days a week, then you will need to get a UPS.  You need to first calculate how much power your system uses and then how long it needs to run while the power is out.  Most of the systems do not have to be on so the UPS is simply a tool to protect the components and with software to shut the computer down if the power does not come on within a specified time.  Depending on how much power the system uses and how long you need it to run without power, a good UPS will cost anywhere from $150 to $600.  American Power Conversion or APC, is a manufacturer of surge suppressors and UPS systems.  They have an excellent section on there web site that will help you to select the right UPS for your system.  The address of the selector is http://www.apc.com/sizing/. 

The next item that you need to keep up with is the cooling of the system.  The computer has a number of fans inside the box to help to keep it cool.  You need to be sure to place the computer in a location that will allow the fans to do there job.  Try to keep the front and rear of the computer free of books, papers and any other debris that would block the airflow in or out of the holes in the box.  This will allow the fans to circulate the air as much as possible to keep the system cool.  Do not forget about the monitor.  Those little holes in the top and sides of the monitor are not for you to hang notes on.  They are to let the air circulate also. 

Dust will also hinder the cooling process. No matter how clean a home or office you keep, you will not be able to keep the dust away from your computer.  There seems to be a dust magnet that is built into all the computer systems in the world.  Every six months you should turn the computer off, pull the box out and vacuum the dust from the holes in the outside.  Inside the box will need to be cleaned out at the same time.  Be sure to turn the system off before opening the box. You can use a can of compressed air to blow the dust out of the cracks and crevices inside the box.  I like to use the compressed air and the vacuum at the same time.  The air will dislodge the dust and the vacuum will pick it up so that it will not make a mess in the house.  The very best way is to unplug all of the cords and take the box onto the patio outside for its biannual cleaning. Pay attention to the areas near the fans, as this is where most of the dust will accumulate.  The fan on the CPU will also cause you the most problems if the dust is so heavy that it effects the cooling of the CPU. 

Make sure to replace the cover so that there are no gaps in the casing.  If there are any holes that have been left open from taking cards or devices out, be sure to fill the hole with a blank plate to help to keep the dust out.  These can be bought from any computer store along with the screws to hold them in place.  This is also true of the plastic covers for the front of the computer.  Make sure that they are all in place to minimize the dust accumulation inside the system. 

The only thing left is to take a moment to talk about the cleaning of the outside of the system.  This would be a good time to tell you all about the customer that brought his laptop into the shop because it would not come on.  I looked at the system and as soon as I pushed the power button, I knew I was going to have a problem controlling my laughter.  There seemed to be somewhat of an oily residue on the side of the computer.  I looked a little closer and found that the residue was on the keyboard and the top and bottom of the laptop.  The next thing that came into my head was to smell this residue to see what it was.  I could not place the smell for a minute and then it came to me.  I looked at the customer and asked him why his computer smelled like WD40.  He said that he used WD40 to clean everything because it did such a good job of taking the grime off.  There was no hesitation when I told him I knew exactly what was wrong with his computer. 

This is an example of what not to use to clean any part of your computer.  If you must use any type of liquid, put a small amount of plain water on a soft cotton cloth to clean the grime off of the outside of the box and the monitor.  You can also use the moist, but not wet cloth to clean the screen. Make sure never to spray anything into or onto any part of  your computer.  Always moisten the cloth if you must have a liquid to clean your system.