mirror the image on a new layer (flip it vertically and align it exactly in place as if the MAC was sitting on a mirror)
set the opacity to some small number so ya can see through it
take the gradiant tool with white to red (or some other color that is obviously NOT in the picture - trust me)
make a gradient from white on the bottom fading to red just at the top of the "shadow" or just below the original picture
set the color settings to change red to transparent so it looks like the shadow now fades into white
adjust the image on this layer and pull the bottom up so that it seems to squish the "shadow" a little
"transform" the "shadow" and drag it off to the left a little
voila