Hello,
From what info you've provided, it's hard to say what the issue is.
However, one good "rule of thumb" is to be sure you have the latest graphics drivers, BIOS, and OS updates installed.
You never mentioned what program you are using to display the video or the specific format for the video; be sure to check the software vendor's site for updates, workarounds, or specific issues that may exist. Many programs also require a minimum system configuration, so check that as well. If the issue occurs with a specific piece of software, try another software package and see if you get better results -- there are lots of software packages out there for viewing videos, many available at little or no cost.
Also, please let us know your OS, and how much RAM/VRAM you have (again, you may not have enough to run the software). Adding more memory is usually one way to help resolve issues, but with older systems a system upgrade may be more cost-effective (especially if you want to enjoy playing the latest games).
Hope this helps!
Regards,
Neal
