File format of sound clip for PowerPoint?

I have to make a PowerPoint video thing for school with audio files of me talking on every slide. On my iPhone, I recorded myself talking in about 15 second clips (I have 4 15 second long clips). I emailed them to myself and saved them to my Windows 7 PC. Then on my Microsoft 2007 PowerPoint I clicked add a sound, and added the clip. But now, the clip wont play because when I try to play it it says "the specified file cannot be played on the specified MCI device. The file may be corrupt, not in the correct format, or no fil"… I don't know what MCI device means and all I want is for my sound clips to be able to play and be heard in my PowerPoint. Is there a specific file type that i have to convert it to or a certain folder that i have to put it in? And how do i do this? Thanks so much!

Read more: File format of sound clip for PowerPoint?