Inserting countdowns into a PowerPoint presentation

For a session that I will present this afternoon, I wanted to add a pair-share activity, but I need to limit the time of the activity as I only have 15-20 minutes in total to present.

I thought, there must be a clever way to add a countdown timer to a slide... please YouTube, show me the way! 

Here is the video that I found and the corresponding PowerPoint presentation with various time gadgets embedded within the slides.  All you need to do is copy and paste the time limit that you want and voila!


http://www.youtube.com/watch?v=XDeRcfhsR2U&noredirect=1 
http://a6training.co.uk/resources_powerpoint.php

Thank you YouTube, you made it incredibly easy to add the counter to my slides!