This viewer is available from Microsoft:
PowerPoint 98 Viewer for Macintosh:http://www.microsoft.com/downloads/details...;displaylang=en
However, there seem to be so many variations of the Mac OS, which may or may not be compatible,
may I suggest that you post your question again in the following forum:
Operating Systems Mac OS.
Hopefully you will get replies from people conversant with the Mac systems and software,
who can also tell you if the above viewer is of any use.