Step 1
Open up a new document, and color the background any color you want. Then make a new layer. Grab the lasso tool and draw out one side of the folder like this.
Step 2
Color in the folder, and go to layers/layer style/ and go to gradients. Now play with the gradients until you get to something you like. Here is what I came up with.
Step 3
Now we need to another side to the folder. Make a new layer again. Grab the lasso tool and draw the second side of the folder just like this.
Step 4
Like you did with the first side of the folder, do with the second and go play with the gradients until you make it to something you like. This is what I did.
Step 5
Go play with the shadowing on second side of the folder. Use the image above to do that.
Step 6
Now add a black 1 pixel border to both sides and make the opacity to 27%. Now you are done. You should have came up with something like this













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