I made a bunch or variations of this for my current psudo-mac setup on my laptop running vista(using multiple icon packs, docks, themes, and 'Vista OS X', along with other things)
It was pretty easy to make. i just followed a tutorial for making a windows vista logo in photoshop, then took out some layers, such as those that give it the blue color, made various versions using different layering of the apple and windows logos, and finished it all off with a nice, simple outer glow