Let's look at some preventative maintenance that can be taken for each of these variables:

First and foremost, backing up your important data can save the most headaches. Using Tech In A Box to make regular backups is the key.

See also:
What Is A Backup?

Human Factor

1. Be careful when moving a PC. Excessive jarring of the case can loosen internal components, and dropping a PC can cause the PC to not power up again or to lose your data permanently from the hard drive. Do not move or slide a PC while the system is powered on.
2. Keep all of your packing materials and documentation/software in a place where you can easily find it again. These items were included to help with problems that may arise.
3. Do not leave small children unattended with a running computer. The lights and buttons entice little hands to explore and probe. An ejected optical drive tray is very vulnerable. Foreign objects inserted into the case can wreak havoc.
4. Get into a habit when downloading and installing software. Always download the software to the same folder and run a virus check on the file before actually installing it.
5. Do not install your programs into the root directory of the hard drive. It is much healthier to create a folder for the installation.
6. Learn how to Uninstall programs you no longer use. This will free up valuable hard drive space and, in some cases, speed your system up.
7. Do not save your data in the same directory as your application. This way your data files are safe if the program directory ever gets accidentally erased or uninstalled.
8. Keep copies of your important data on some other media, away from your computer.
9. Keep a log of software and hardware changes you make. If you need to consult a support specialist, this information may be important.
10. Before making a change to anything, make a note of what the setting was before you changed it. This will make the process of undoing any changes much easier.

Environment

In a perfect world, your computer should be in a humidity controlled, dust free room. So what can be done to help with the environment in the "real world"?

1. Don't place the PC near a heating or cooling vent. Any extremes in heat or cold can damage a PC, especially over time. It is important that the vents on the computer are free of obstacles that could impede proper airflow of the cooling fans and vents in the PC.
2. Don't place the PC where water can splash on it. Don't place the computer near an open window where rain can reach it or under plants where watering can drip onto the PC.
3. Do not plug a computer or external components directly into an AC outlet. Surges and spikes in the AC line can damage these sensitive electronic components. Always use a surge strip or similar protection.
4. Do not place the computer near strong magnetic fields such as electric motors, home appliances, fuse boxes, fluorescent lights, etc. These magnetic fields can cause intermittent errors, distortion and discoloration in a CRT monitor, or loss of data from magnetic media such as floppy disks or the hard drive.
5. Keep the computer clean. Dust buildup can impede the important airflow in the computer and cause the system to run more slowly, or shorten the life of internal components. Use canned compressed air (the type designed for electronics) to dislodge dust from internal components. Do not blow compressed air directly into a floppy drive as the flying debris can lodge on critical internal parts and cause the drive to malfunction. If you are uncomfortable removing the case cover for this type of maintenance, you can have it cleaned professionally. Do not use a vacuum cleaner inside your PC. Aside from causing damage by inadvertently removing small internal components, there is a static charge potential that can cause damage to your PC.

See also:
Cleaning a Mouse

Cleaning a Keyboard

How To Clean A Flat Panel Display

Software Glitches

1. Always install software from the original disc if possible. Be cautious of software downloaded from the web or given to you by other people. At the first sign of a problem, uninstall the software and verify all of your steps before reinstalling. If the problem reoccurs, you may need to consult the documentation or software vendor for troubleshooting steps.
2. Always verify that the software you install is compatible with the hardware and operating system in your PC.
3. Be careful what software you allow to install from the Internet. There are many "Spyware" programs that can attach themselves to your system that not only track and report your Internet surfing and buying habits, but also run in the background causing your system to slow down, sometimes to a crawl.
4. Always check the condition of your optical discs. Scratches and cracks can make them unusable. Use care when storing optical discs. Use jewel cases or sleeves to protect the discs.
5. Regularly run Scandisk and Disc Defragmenter to check for hard drive errors and to keep your hard drive running at top speed.

Virus attacks

1. Viruses are software programs specifically written to do something that the user had no intentions of doing. These processes can be non-harmful or they can be devastating to your PC and possibly everyone else your PC comes in contact with. Always run a virus protection software. Try to choose one that does real-time scanning. Real-time scanning will alert you of viruses at every entrance point to your system and allow you to quarantine or delete these potentially dangerous files before they can launch. Keep your virus definitions up to date. These definitions can change daily in some cases. Virus software that automatically updates it's definitions are the best choice.
2. Virus software is only good for viruses that are known. You can still be vulnerable to the attack of a brand new virus that is undiscovered. That's where a backup of important data is essential if a virus attack cannot be undone. You also need to make certain the backup you have is not virus infected. Always run a virus scan of data before backing it up.
3. Spyware is not the same as a virus, but can be a real nuisance. Spyware gets installed, normally while you are on the internet, without you knowing about it, and runs in the background collecting data about your computer habits and sending this data to marketing firms. Since these processes use up your computer resources, spyware can cause your system to run slowly or to cause intermittent errors while running your programs. Web sites that offer tools for removing spyware are Microsoft Windows Defender and http://www.lavasoftusa.com. This is not an endorsement for this particular software, merely a nudge in the right direction. Technical Support cannot offer free support for the use of this or any other software that did not come installed on the system.
4. Internet Browser Pop Up windows. These are very aggravating when you are surfing the Internet. One way to stop these pop ups is to install some sort of pop up stopping software. Use common sense when selecting this kind of software - do some research to find a reputable program. Also be aware that stopping some window pop ups can cause problems with legitimate programs trying to run, such as Windows Update. When you have a pop up stopper running, learn how to defeat it in case it causes problems.

Hardware malfunctions

1. Sometimes hardware just fails. Sometimes it doesn't fail, but appears to fail because of some software or another piece of hardware that was introduced into the system. Always keep a list of changes in hardware and software. If something happens, you can look at your list and decide if the problem started to occur around the date that something new was added. When adding a new piece of hardware or software, make sure you have contact information for the company that manufactured the new item, they will be the best source for correcting a problem.
2. Sometimes in the process of installing new hardware, you may have loosened an existing piece of hardware. The first step in troubleshooting problems that occur immediately after installing new hardware is to verify that no existing cables or cards are loose. As an additional troubleshooting step, you may need to remove the new hardware to see if the problem goes away without the new hardware installed.
3. Be sure to read any documentation that was included with new software or hardware. Some problems are well documented and easy to correct. A lot of problems with new hardware arise from improper installation of the software drivers. Read the documentation carefully for the operating system you have, to make sure no steps were missed during installation.
4. Many hardware malfunctions occur right after moving a PC. Always be gentle when moving and setting down a PC.