What is Spyware?
How to protect your PC
Watch this video.
Some Images from the Video
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If you are using Windows 95 or windows 98 or windows NT, you have to upgrade it to the latest version.
Windows XP(with Service pack 2 and with firewall facility in XP turned on) is very good.
To check whether the firewall in XP is turned on, Click Start > Control panel > Windows firwall > Now check the 'ON' radio button is selected.