Adware installs itself on your machine usually through another program. The most common source of adware is when installing a p2p filesharing client, or other 'free' software. While these programs install themselves on your computer, they also install adware software that takes up system resources and keeps sending you those annoying ads.
To free your computer of ad adware, the process is very similar to cleansing it of viruses: the first step is to remove the adware, then to focus on preventing the adware from returning. Fortunately, most of the best adware software is free, so removing it should be a fairly simple process for the average user.
The first step is to download ad adware program. There are many free adware programs. Currently, Microsoft AntiSpyware is in beta release and is offered to current users of Windows XP free of charge. For a long time, the best adware software was called Ad-Aware, which has a free personal edition. This software is still very good, although it does sometimes have trouble with browser hijackers, which are irritating applications that misdirect your web browser to sponsored sites.
Regardless of your choice, it is now a matter of downloading the chosen adware application and installing it. Most adware software, like antivirus software, relies on constantly updated definitions files, which allow it to seek out the newest types of adware. Once your software is installed you will usually be asked to update the adware definitions and then perform a scan of your machine. Many users are surprised to see how much adware turns up on their initial system scan.
After scanning your machine for the first time, it's likely the adware application will have come up with a large list of registry entries and software that must be removed. Once this is done, the user is often asked to reboot his machine. It is important to accept this advice and reboot as soon as possible: one of the irritating traits of adware is its ability to continually regenerate itself in the operating system, and as soon as the adware related registry entries are removed it is import to do a 'clean' reboot of the system.
With this first step - cleaning the system of adware - complete, the user must focus on keeping the system adware free. This most important step is accomplished by using a 'live scan' feature that is present in most adware software. What this feature does is loading a small application when the computer boots, and this program monitors computer activity and looks for any adware related activity and blocks it before it can cause any problems for the user. This is a transparent process, and most users with newer PCs won't notice any performance effects.
Following the steps outlined above, the average user will have little trouble removing adware from their system, and preventing adware in the future. Like all software, adware software is never foolproof, and the user is still advised to take sensible precautions, such as researching what software they install, and always clicking "No" to internet explorer windows that ask to install software.