If you don't have Powerpoint, you can download a PowerPoint viewer at the Microsoft office website.
http://support.microsoft.com/kb/126492
The viewer allows the presentation to be seen, but not altered. Some advanced features, like embedded files and such, may not be supported, but I doubt if you would need that capability.
Windows 7 is an operating system. It will only support the software that is on it. If you don't have an Office suite with PowerPoint (or some other program that will open PowerPoint files), you can ask the PowerPoint show's creator to "Pack 'n' Send" it so it can be seen without a viewer or the program. I should warn you ahead of time, this creates a huge file size!