One of the most common format of electronic presentations is the .ppt (Microsoft Power Point).
As you may know .pps files can be open with Power Point software from the Microsoft Office suite. Microsoft Office is a suite of software that is not free. Therefor, if you only need to view this presentation files you have to know that Microsoft offers you a free option: Microsoft PowerPoint Viewer.
PowerPoint Viewer lets you view full-featured presentations created in PowerPoint 97 and later versions with full fidelity. This viewer also supports opening password-protected Microsoft PowerPoint presentations. You can view and print presentations, but you cannot edit them in the PowerPoint Viewer.