It's possible that they aren't videos at all and are merely links that once you click them, a virus will be downloaded. Otherwise check you have appropriate codecs and drivers downloaded to play videos. Search for "windows 7 codec pack" and theres a download from CNET (trusted source) download that one and install, then try again. Personally i never click on any links in Facebook now, not even from friends unless they actually tell me it's their video. It's all good and well me saying this but until you actually have a hard drive wiped due to clicking on an erroneous facebook video link that drops a virus into your system, then you won't really appreciate it.
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