Install VLC Media Player
If your PC is a Win10 machine, use the Windows 64-bit option. If it's a Win7 machine, you might need to use the Windows download, but it might be best to ask your IT person to be sure.
Once you've downloaded it, you'll need to install it. As it is downloading, you can click on the down arrow and choose Open when done and it will open the install program once it is done downloading.
(Or, if you click that arrow after it's downloaded, the option will just say Open.)
Click Run, then click Next for each option until it starts to do the installation. Once it's done, uncheck the Run VLC Media Player option and click Finish.
After you've installed it, you'll want to associate that program with the .mp4 file type extension. To do that, go to the start menu and type "file type". You'll see some options under Control Panel that say:
Either of these options will take you to a list of your file type extensions.
Now look through that list for .mp4.
Click on the .mp4 extension and click the Change Program button toward the upper right corner.
Click on VLC media player and then click OK.
Once you've done that, try to play the video again. (Note that if you already had the video opened, close it and click on it again. This time it will open in VLC Media Player.)
If you have any trouble, Lisa can assist you. Send an email to firstname.lastname@example.org or call her at the office number.