Here's how not to get a virus:
Don't run keygens
Don't pirate software
Don't run any software that is supposed to help you cheat at something or get something for free that you would otherwise have to pay for.
Don't install video codec packs
Don't install toolbars
Don't use internet explorer
If you want to watch research, save the video file and open it with
VLC. If it won't play, throw it away and move on.