ANSWER: Dear Virginia,
thank you for your question.
To open your .pps (PowerPoint Show) files you will need the PowerPoint viewer. You can
download the PowerPoint 97 Viewerhere (or here for more recent PowerPoint versions).
If you have a Mac please find the Viewer here.
Alternatively, you can also use PPPCD, a software to save your presentation on a CD-ROM, while automatically integrating the PowerPoint Viewer.
Download PPPCD free version here.