a. Create a New Raster Layer   

     1) Click Layers then New Raster Layer...

           On the Layer Properties Box [General Tab]:
           Layer
           Name = DROP SHADOW
           Blend Mode = Normal
           Opacity = 100
           Group = 0
           Layer is visable = Checked
           Lock transparency = Unchecked
          Mask
           Mask is enabled for this layer = Checked
           Mask is locked with layer = Checked

     2) On the Layer Properties Box
         [Blend Ranges Tab]:

           Blend Ranges
           Blend Channel = Grey Channel
           This Layer: = Default
           Underlying Layer = Default