I've had Photoshop 7 since it first came out, but have only dabbled lightly in it a couple of times.

I am trying to make a background picture to use in Poser (I have have both 5 and 7) of a subsurface view of an ant colony with an abouve ground view too.  I created the scene using two layers with heavy noise filter for the subsurface ground texture and ligt noise for the background of the tunnles, then erased the aboveground view on the layer with the light noise.  I'm left with a .psd file as a background in Poser in which I need to make the above ground portion transparent in Photoshop so I can add aboveground elements elements (plants, peiple, etc.) in Poser and not have them show against the white aboveground background.  I can use the magnetic lasso tool to select the white aboveground view portion in Photoshop, but I'm stuck knowing what to do next to make this portion transparent in the final .psd file for imprtinging into Poser.

Intel Core I7 3090K 4.5 GhZ (overclocked) 12-meg cache CPU, 32 Gig DDR3 memory, GeoForce GTX680 2gig 256 Bit PCI Express 3.0 graphic card, 3 Western Difgital 7200 rpm 1 Tb SATA Hard Drives