PowerTalk

PowerTalk was designed to be a free program that automatically speaks any presentation or slide show running in Microsoft PowerPoint for Windows.

You just download and install PowerTalk and while you open and run the presentation as usual it speaks the text on your slides. The advantage over other generic 'Text To Speech' programs is that PowerTalk is able to speak text as it appears and can also speak hidden text attached to images.

Speech is provided by the standard synthesised computer voices that are provided with Windows.