If your computer needs to install software to watch a video, don't do it. Better safe than sorry.
Grisoft Ewido Anti-Spyware is very good at identifying and removing spyware from your PC. We recommend trying the online or free edition for starters.
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A complete guide to battling spyware, including reviews of twelve antispyware applications, downloads, FAQ, a spyware glossary of terms, and other helpful resources.