
Backup important data
A computer or its hard drive can fail at any time and without warning. When it does all your personal documents, letters, pictures, music, video, etc. is lost and in many situations cannot be recovered or costs a lot of money to be recovered. Make sure you have backups of all your important data so it is not lost when the computer fails.

Protect the computer
Make sure to protect your computer from electrical surges, brownouts, and black outs. At the very least, every computer user should have a decent surge protector on their computer and phone line if they use a modem. Surge protectors can help protect your computer during an electrical storm and could save you hundreds of dollars in repair, if it were to get damaged. It is also a good idea to have the computer running on a UPS, which can help prevent damage to a computer during a brownout or blackout.

Keep computer and its programs updated
There is no such thing as a perfect software program or hardware drivers. After the developer has released their program they may discover errors and release updates to fix these problems. In the case of major software programs and operating systems, there can be several hundred updates and service packs released during its life time. Making sure your computer and its programs are up-to-date can help prevent problems.
In addition to updating a program, programs that use other programs or plugins may also need updates, for example, it is very important to make sure all the plugins for your Internet browser are also up-to-date.

Keep the safe from viruses, spyware, phishing, and spam
Every computer connected to the Internet or other network need to be protected. If you're using Microsoft Windows, we recommend having some form of antivirus program installed and running on the computer. It's also a good idea to have a malware detection program running on the computer to pickup any spyware or malware that an antivirus may not have detected. Finally, every computer user should also be fully aware of other security risks such as chain mails, phishing, and spam while on the Internet.
Source: http://www.computerhope.com/