What is happening now is that the overly large size of the picture is
overlaying the slide and you can't see that only a part of it will show
during the presentation. While this trick can be used for some great effects
with motion paths, it sounds like what you want is to just shrink the
picture.

There are two easy ways to do this. First, you can select one of the corner
handles on the picture and move inward towards the center of the picture.
This will shrink the picture proportionally and give you control of how big
the picture should be. The second way is to select the picture, right click,
and go to Format, Size and Position tab (PPT 2003 and earlier) or Size and
Position. Once there, you can adjust the size and location of the picture to
fit on your slide.

Does that make sense?

Yes it makes sense but although I resized the pictures on the slide, when I
view the slide show the picture(s) are enormous. What is causing this?
Thanks