Try using the window frames and shadows from the windows 7 theme,see what happens,might have to edit the corners of the window frames with an image editor to make them blend into the shadows better.As the frames are designed to be square in windows 8 you might not get this to look perfect.
Locations
Windows & Caption Buttons > Aero > DWM Window > Frames > Window -top,bottom,left,right
Windows & Caption Buttons > Aero > DWM Window > Frames > Details > Shadows - top,bottom,left ,right
Find more detailed locations here >
http://vistastylebuilder.com/forum/index.php?topic=1536.0