I can't answer the part about no sound, because I just made a PP (.pptx) with sound, and when I opened it with KN, the sound worked fine. So my guess is that the attachment you've been sent has been sent without the sound file. To be able to play a PP doc which includes media (audio, video) on any computer other than the one on which it was created, whether Mac or Windows, whether opened with PP or KN, it must be saved as a
package (which is a folder containing the PP doc plus the media file), and the whole package must be moved (whether by email or memory stick) to the new computer. The same thing is true with KN docs, BTW.
Moving on: If, on a Mac, you're clicking on a PP doc but it opens in KN, that's probably because you don't have PP installed. Is that the case? If you don't have PP, but want to view a PP doc in PP, or, in any case, not in KN: there used to be a Microsoft app "PowerPoint Viewer for Mac", but that doesn't work with OS X, and there's no update. If you don't want to buy PP, I believe NeoOffice, which is free, will open PP docs, and even allow you to work on them. Obviously, buying PP (MS Office) is the surest, but most expensive solution.
Now then: If you
do have PP on your Mac, but your PP docs nevertheless open in KN, it sounds as if the default app for opening PP's has been reset wrong. Correct this by: "Get info" on that file; halfway down the window which opens is an "Open with:" drop-down, where you can set the default app back to PP, and click below that to apply this change to all files like this.
Just out of curiosity: what do you mean by "working version, not the finished product"? Is the difference only the missing sound, or is there more to it than that?
Good luck.