Adding sound to PowerPoint presentations

Someone asked me about adding sound to a PowerPoint presentation. I had no clue how to do it. Apparently, it's not as straightford as I thought it might be. YouTube has a couple of good videos explaining what to do step by step:

http://www.youtube.com/watch?v=9zDoa3H5TUs

http://www.youtube.com/watch?v=Zdig4XLUpFE

See also the library resources on PowerPoint 2007.

Fun!