Video's skip for many reasons. Most of the time the processing power of the cpu is not great enough for smooth playback. Close all other programs when viewing videos.
You can decrease or eliminate this problem by closing all running background programs on your computer, if this does not work maybe setting your graphics card to use a lower number of pixels can solve this problem. If this still does not work I would suggest upgrading your processor or video card.
This depends on what the videos are, what you're playing them with, and if they're streaming from the internet. File sizes, old hardware, and internet connections could all contribute.
