How to show a Keynote presentation on other platforms?
From your Keynote document select:

File &gt; Export &gt; PPT...


or better (to avoid most problems with PowerPoint format):

File &gt; Export &gt; PDF...


This last format will work perfectly on any Unix and any Windows.

Warning: test these formats on the target system before a serious presentation.

With both formats, video, animation, transitions and presenter notes will be lost.

If your projector is of the VGA era (see https://www.google.fr/search?q=vga&amp;source=lnms&amp;tbm=isch) then I would advise you to:


Stay with Keynote (this software is still many years ahead of many others and mostly of PowerPoint).
Buy a Mini DisplayPort to VGA adapter.