This tutorial was made in French by cool-rabbits. You can find the original tutorial here. 
Thanks for the good tutorial! 
My job in this was to translate it into English, I hope you enjoy it! 
Two things motivated me to put some hours in this. 1) the quality of the original tutorial and 2) the request of a pretty new and nice English forum member. Right, here we go, hold steady!
Create an avatar/signature pack Vista 3D:
A/ The base.
1) We’ll start with making the avatar. Create a new document with a size of 256 by 256 pixels, transparent background. Call the document « Avatar Vista3D ». Zoom in to 200%.
2) To help you see the different effects (size of the shadow, external effects, etc.) fill layer 1 with a white color. Use Alt+Backspace to fill the layer fast. Create a new layer (Ctrl + Shift + N).
3) We’ll use the rulers to center our avatar. First, show the rulers (Ctrl + R). Click on the left measure bar and drag to the right. Use the Shift key to the 4th little stripe on the ruler. Repeat this operation on the other rulers. You should obtain the following result (all previews are posted with a 100% zoom, so the rulers are a bit different!
.
4) Select the Rounded Rectangle Tool, with a radius of 10 px. Create a rectangle, with help of the rulers, just like this (use the 1st of the three options (Shape layers), and select black as your foreground color):
5) Select the Movement tool (V) and choose Edit -> Free Transform Path (or Ctrl + T). Use the Ctrl key to change the upper left and right corner. Apply a transformation like this:
6) We are still in the Free Transform option. Now flatten the rectangle as in the picture (it doesn’t matter what edge you take (up or down), because you’ll have to hold the Alt key):
7) Without leaving the Free Transform option, use the Shift key and the up arrow to move the rectangle 10 pixels up. You can now click Enter to apply the transformation(s).
8 ) Now you’ll start seeing the 3D shape. Duplicate layer 1, and place the copy under the original layer. Hold the Shift key and move the duplicated shape 10 pixels downwards (make sure the movement tool is selected). Once you remove the rulers, you start to get a general idea of the shape in 3D. A small defect ruins the impression for us, it is circled on this picture:
9) To correct this mistake, we’ll use the Pen Tool (P). But it’s necessary to rasterize the two shapes first. To do this, right click on a mask and select ‘Rasterize Vector Mask’. Do this for both layers. Once you are done, create a shape like this:
10) Right click the path, and select ‘Make Selection’ (Anti-aliased, Feather radius: 0 pixels). Fill the selection with black (make sure your active layer is the original layer). Repeat this operation on the other side (right).
11) Select layer one and hold Ctrl while you click on its thumbnail (this will select the layers objects). Go to Select -> Modify -> Contract, contract by 15 pixels and hit delete. Do the same for the duplicated layer. If you select the first layer, you can clearly see the 3D shape:
12) Before we begin with applying several effects (crystallization, shadow, etc.) select the duplicated layer. Ctrl + left click on the thumbnail of layer 1 to make this a selection and hit delete (you should have deleted something from the duplicated layer now). This will have influence if you apply a transparency effect.
B/ The effects.
1) We will start with the crystallization.
2) Create a new layer. Then Ctrl + left click on the thumbnail of layer 1. Go to Selection -> Modify -> Contract, and contract by 1 pixel. Select the Gradient Tool (G) (make sure the gradient color is white to transparent) and make a gradient like this:
3) Now select the Rectangular Selection Tool, and make a selection like in the image. Then hit delete.
4) Reduce the opacity to 40%. Select layer 1 and contract with 1 pixel again. Create a new layer and apply a new gradient from white to transparent, like in the picture:
5) Make a selection as in the image below. Hit delete and set the opacity to 40%.
6) You should have something like this:
7) Create a new layer. Ctrl + left click on the 1st layer and fill with white. Click on Select -> Transform Selection. Hit the up arrow twice (this will move the selection upwards by 2 pixels), then hit delete. Reduce the opacity to 70%, we now have something like this:
8 ) Now to the lower part. Place a vertical ruler in the centre of the image (at 180 pixels). Control + left click on the thumbnail of layer 1, and create a new layer above layer 1. Select the Gradient Tool (from white to transparent). Trace a gradient to arrive at the central indicator. Reduce the opacity to 30%. (I am not 100% sure about this translation, hopefully the image helps you a bit!
9) Select the duplicated version of layer 1 and create a new layer. With the Gradient Tool, draw 2 small layered gradients as seen on the picture below. After this, hit Ctrl + Shift + I (invert selection) and hit delete. Now all gradient parts are inside the avatar. Reduce the opacity to 65%.
10) At the finish, we’ll add a drop shadow. Create a new layer above layer 1. While holding Ctrl and Shift, click on both the thumbnail of layer 1 and duplicated layer 1. Fill with any colour you like and lower the opacity to 0%. Open the Layer Style box and apply a shadow as seen below:
Drop_shadow_copy.png
11) To achieve the Aero look of Vista, we have to apply a light transparency to the framework. To do this, lower the opacity of layer 1 and duplicated layer 1 to 70%. Hopefully you’ll see something like this:
C/ Apply a background.
1) To do this, start with opening the picture that you wish to have in your framework (Windows Vista wallpapers will do great, as well as most landscapes). With the Movement Tool, slip it into your .psd document.
PS: I recommend you to create a group called ‘Background’ underneath the lowest layer, where you will put all the following (as well as the first step).
Place the background in the folder and transform and place it in a nice position.
2) Reduce the opacity of the first layer and the duplicated first layer to match the dominating colour in the background, I chose 65%.
3) To restore the Aero style of Vista, it is necessary to apply a Gaussian Blur to the picture that is located under the now transparent borders. To do this, first duplicate the background picture (Ctrl + J). Now apply the Gaussian Blur of around 3 pixels (Filters -> Blur -> Gaussian Blur). Now Ctrl + left click on the thumbnail of the layer above the group called background (if this is the layer where all shapes are on, so you select everything). Hit Ctrl + Shift + I (invert selection) and then hit delete. Now hit Ctrl + E to merge it with the other background image.
4) To cut the background to the size of the framework, we have to make a new selection. Use Ctrl + left click on the layer where all shapes are on. Select the Lasso Selection Tool (L) and, while holding Shift, make sure the selection looks like this:
5) Still at the background layer, use Ctrl + Shift + I (invert selection) and hit Delete.
6) As you can see on the previous picture, the result looks pretty well (for those who want, you can find the wallpaper here). We will finish this avatar by applying a small text. Create a new layer above all layers and select the Text tool and write your text where you want it. I chose to corner it on the bottom right. I used the font ‘Segoe UI’ (standard with Windows Vista), with a size around 30 points. I applied a white external glow and a drop shadow, but you can choose your own style.
7) Now nothing more rests to save the picture as .png, reduce the image size to 128 by 128 pixels and use it as an avatar on CrystalXP!
My final result:
With a little bit of variation, results like these are possible too:
You can of course use your own background picture, different opacity, thickness, color, etc!
If you want to create a signature, it is smart to create a document with the double size of the size of the image you want it to be (560 by 140 for CrystalXP).
I hope that this tutorial has motivated you to do more. You can post your opinions, critics or congratulations here. 
Do not forget to post your realized creations! Thanks again to cool-rabbits for the tutorial!
Thanks everyone for the positive comments so far, to see these comments.. it makes it worth the trouble. 
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