A family of Microsoft presentation graphics products that offer tools for creating presentations and adding graphic effects like multimedia objects and special effects with text.
Not as such in 2007 but you can try this.
Start with a blank slide and right click > Format background. Choose a picture backgrounsd (your photo)
Now place a circular shape over the part you need.
Right Click the circle > Format shape and choose slide background fill (no line)
Right Click again and save as picture (Choose PNG)
You should now have a circular picture saved that you can use.