Barry,
These are quite common these days, as Bunkerbarge quite correctly says above, more commonly used by businesses for presentations and training these days...you know for those overhead projector slide presentations usually done from a computer....your file should have an extension of .ppt to confirm it is a powerpoint document.
It is an excellent package to use, OpenOffice will also open these files as it is Microsoft compatible...OpenOffice is completely free though but is a big download at 104mb from
www.openoffice.org.
There are some excellent joke powerpoints doing the rounds at the moment, I have quite a few.
Nothing to worry about.
Regards...........Mark