I'm going to take a SWAG here and guess that the PowerPoint file was created
on PPT 2007 and has the extension of PPTX which would not be able to be
opened by the earlier version of Presentations that you have. You would
probably either need to upgrade Presentations to its latest version, http://www.corel.com/servlet/Satellite/us/en/Product/1207939618939#tabview=tab2,
or have the person that sent the file to you save the file as a PPT '97-2003
file.
If it is, in fact a PPT file extension, find out from the producer what
version of PPT was used to create the file.