When I go to that page the Slides link doesn't point to a zip file but a pptx file, as I suspected. Here's the link I see:

http://video.ch9.ms/sessions/mms/2013/UD-B326_Agerlund.pptx

Not sure why there's a difference, but in your case you don't have to download anything again, just rename the UD_B326_Agerlund.zip to UD_B326_Agerlund.pptx and it will open in PowerPoint.