Performing routine maintenance on your computer is similar to performing maintenance on a car. If you do so on a regular basis, it will continue to run smoothly. However, if you do not, it will cease to function properly and eventually might stop working altogether. You must clean out your computer periodically to eliminate excess files, get rid of viruses and spyware and keep the computer in top working condition.

Delete Unnecessary Files

Over time, you may download plenty of programs that you are not using; programs that take up hard disk space and slow the computer down. There are a couple of ways you can go about eliminating these files: Click the "Start" button, then "Control Panel" and go to "Add/Remove Programs." This will show you all the programs you have downloaded and how many megabytes of space they use. Select the programs you do not use and click "Remove." This will uninstall the program, therefore creating more space. To delete temporary files, remove cookies and email history that your browser cannot clean, use "CC Cleaner." Download this free application at ccleaner.com.

Viruses and Spyware

Spyware and viruses can cause your computer to operate at slower speeds and eventually crash. There are a variety of ways you can obtain this malware: downloading corrupted music files, opening infected pop-up advertisements and opening emails from people you do not know. Fortunately, there are many programs you can download off the Internet for free or a nominal feel. One of the best and most well-known is AVG free anti-virus. Comodo and Avast are also anti-virus programs that can be downloaded for free. To get rid of spyware, programs such as Counterspy and Adaware are helpful, too, but you have to purchase them first. Run a scan on your computer at least one to two times a week. This will detect any viruses or malware that may be dangerous to your computer and allow you to eradicate them.

Defragment

Defragment your computer every once in a while to align files on your hard drive. This allows the files to be accessed more quickly. The Windows operating system has a Disk Defragmentation program installed. To access this, click the "Start" button, select "All Programs," select "Accessories," select "System Tools" and then "Disk Defragmenter." When files have accumulated over a period of time, they get scattered and cause your computer to slow down: defragmenting them will rearrange them to speed up your PC. This process may take one to seven hours to complete, so only do this when you know you will not need to use your computer for that length of time.

Source:

microsoft: Restore Your Computer's Performance with Windows XP

webtechgeek.com: Clean Up & Free Up your Computer Hard Drive Steps!