Not enough info is given to answer which is why I think no one has replied.
What type of Computer Desktop or Laptop, what version of windows, is it 32bit or 64bit, type of video card or is it onboard.
How old is the system, program used when issue happens playing videos. Is video on your system or do you me playing from youtube, If on system is it every type movie avi, mpg or other, do you mean dvd or bluray disk, Do you have virus protection and which one, do you have malware protection if so which one. Do you have all windows update applied.
What codecs are you using?
When was your computer last cleaned inside case?
when was last time you used disk cleanup? when did you last defrag your drive? Is your drive SSD or HDD.
You also say videos are shutting down your computers, so how many with same info I listed above?
Do you play games with heavy graphics?
Is you version of Windows and the videos legal?
The list can go on but those are what a person need to know.