A handy and free tool to help you remove spyware and adware is Windows Defender. It should already be installed if you run Windows Vista. If you’re running Windows XP, you can download it for free from www.microsoft.com/defender. Here you can read more about it, as well as download it for free. After you've installed it, it will be located in your Start Menu
There are couple of things important to note. First of all, look at the Definition Version. You want to make sure that the date is a recent date. This ensures you have the latest updates.
You also want to be able to scan your computer. You can do this by clicking on the drop down menu next to 'Scan'. Here, you can perform a Quick Scan, Full Scan or Custom Scan. This will allow you to determine which files and folders to scan.
If you want to configure Windows Defender to perform a scan on a regular basis, go to Tools, then click on Options. Here you can set Windows Defender to scan your computer on a regular basis. Make sure that the first check box is clicked, and set your settings below. Once you are done, click on the 'Save' button.