[MadlyAlive]

If you have images in the PPT, then double click on one of them, go to the Picture tab and then click compress. A dialog box will pop up and ask if you want to compress that 1 pic or all in the document. Choose all and then choose Print. Apply it and then save as a different document name. Check the file size then. If it's still too large, go through the same process, but choose Web/Screen.

This usually doesn't change the quality of the images too much, but I would go through it just to make sure.