Fill 0% on the layers.
Blending Options-Gradient Overlay

Create Microsoft Windows Vista Wallpaper in Photoshop CS

Gradient?s parameters:

Create Microsoft Windows Vista Wallpaper in Photoshop CS

Make three copies of the new made layer and make use of the Free Transform option
to make the copies smaller, like they are shown in the picture from below:

Create Microsoft Windows Vista Wallpaper in Photoshop CS

Using the last instrument, it?s possible to draw the lateral flare.

Create Microsoft Windows Vista Wallpaper in Photoshop CS

Create Microsoft Windows Vista Wallpaper in Photoshop CS