Keynote and .pps files

My PC friends keep sending me emails with .pps Power Point slideshow files attached. Keynote won't open them. I can click on Quick View, and Preview will open them, but not as a slideshow, and any audio is missing. In a few cases, I have been able to change the filename extension to .ppt and have Keynote open the file. But that only works sometimes.

I really don't want to install Power Point for Mac on my machine.

What are you guys doing about this problem?

Have you tried Open Office? They open PPS files just fine for me.