Create Microsoft Windows Vista Wallpaper in Photoshop CS

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 this new made layer and make use again of the Free Transform selection to make the copies smaller, keeping the given proportions and parameters.

Create Microsoft Windows Vista Wallpaper in Photoshop CS

Blending Options-Gradient Overlay (for the red sphere)

Create Microsoft Windows Vista Wallpaper in Photoshop CS