Embedded PowerPoint images can be quickly extracted with a little trick from technology blogger Amit Agarwal:
To extract pictures from the PPT slideshow, all you have to do is export the Powerpoint Presentation as an HTML web page (File -> Save As -> Select .html from the File Format drop down). PowerPoint will automatically extract every picture embedded in the PPT file and save it to the local folder. The same technique is also used to extract sound from presentations.
A quick and easy way to get all those images at once.