Step 3 - Adding The Gloss
For this step, the first thing you want to do is create a new layer, you can name it anything but for the purposes of organization we will be naming it "Gloss".

With this new layer selected, so everything you do goes on this layer (Having multiple layers allows you to add a logo under it later on.) Once again, Ctrl+Click the circle layer thumbnail, it should select the circle but the layer you just created should remain selected. On your top menu bar, go to

Select -> Modify -> Contract: 5px

This creates the outline of where the gloss will go. The creator of the Vista logo (assuming he used Photoshop) modified this selection a bit to give it a more rounded effect. This tutorial is for beginners but for the more advanced this is easily achieved by right clicking the selection and going to "Transform Selection" and nudging both sides in a few pixels.

With the Gloss layer selected, and with the selection you just created, go to

Edit -> Fill -> Color: White, Blending Mode:Normal, Opacity:10px

Congratulations! You now have the basic gloss done. Do not deselect yet, the fancy footwork comes in the next step.