If CK-12 videos are not playing on your Windows device and resembles the image below, please update your Windows software to the latest version. Also, make sure the appropriate video plugins, such as flash, are up-to-date.
Screen of a video not playing:
If you are running Windows 8.1 or below you will need to update.
Note: We always recommend keeping your system up-to-date with the latest version available. Check out this page for browser and operating sytem info if you are unsure what version you are using.