One of the most common computer problems users complain about is that their system runs slowly. Slow start-up, slow internet, slow file access, or just plain "slow". If this sounds familiar, the problem could be that you simply have an old system, or if it once ran faster, it may be another problem. The following are some of the most common causes of a slow-running computer and what you can do about them.
Programs have built up over time. Over the last several months or years, you've probably downloaded programs to track stocks, watch the weather, instant message, play music, whatever. Often these programs are set to run automatically in the background which results in a slow-down in your system. To disable programs that you no longer use, click Start > Run and type "msconfig". Then click on the Startup tab. This procedure produces a list of the programs that start each time Windows starts. Most of these programs are unnecessary and can be prevented from starting automatically by simply un-checking them in the list and rebooting.
Temporary files. Through the course of browsing the internet, a variety of temporary files are created. You don't need most of these files for everyday use, so delete them. While on the internet, go to Tools > Internet Options > Temporary Internet Files.
Full hard drive. You can check how full your hard drive is by right mouse-clicking on your "C" drive and selecting "Properties". To alleviate the load, try defragmenting on the Tools tab. For a detailed description on defragging, check out http://computer.howstuffworks.com/question548.htm.
Not enough memory. If your computer can run older programs fine, but struggles with newer programs, then you may want to upgrade the memory (RAM). This is fairly easy to do and may well be worth the additional investment, but may not always solve the problem depending on the age of your system.
Adware and spyware. Adware and spyware enter your system while using the internet, generally as a component of another program, and usually unknown to you. Once in your system, adware serves up a constant stream of advertising (i.e. pop-ups) while spyware, on the other hand, gathers information on your use of the internet usually for advertising purposes. Removing adware and spyware is no easy task, but is highly recommended. There are a variety of products available to help remove these nasties that are worth a try, such as Spybot and Adaware.
Viruses. A virus is programming that is installed on your computer without your consent or knowledge, and is generally designed to replicate itself. Viruses most often enter your system via email attachments or downloads. At the very least, these nasties negatively impact your computer's performance; more sinister versions change, erase or capture your data. To prevent viruses in the first place, install anti-virus software such as Norton or McAfee and keep it up to date, exercise reasonable caution when opening email attachments, and turn off File Sharing. If after all of this your PC still becomes infected, you may need professional help, but first try one of the commercially available virus-removal programs.