Making a drop shadow from a scanned image?

[BeesKnees]

How do I create a drop shadow of a scanned image in Photoshop or Photopaint?

I've scanned a painting of a pine cone on a white background and want to add
a drop shadow. Is there any way to do this in Photopaint? The problem is I
can't select the cone as an object and separate it from the white
background. Any ideas?

 

[BeesKnees]

Thanks but I must be going wrong. When I pull down layer (in Photoshop 8) and hit "new layer" all the options including drop shadow are greyed out. If I create a new layer using background (ie the scan) I can then set drop shadow settings, but nothing happens - it seems to be treating the whole image including white background as a solid rectangle

 

[BeesKnees]

Ah - there's the problem. The outline is extremely complex and would take weeks to pick out using the selection tool. I've tried creating masks automatically but I can't get that to work either.