Other transparent Windows 7 Start Orbs in PNG format have shadows and other artifacts (eg the one with ViGlance). This is because they used an eraser to remove the background.
However, this one is perfect.
I have used the alpha 1 channel as a mask for the main image by copying the alpha channel and making a mask. I have provided the source PSD for educational purposes.
This technique can be used for converting almost any Microsoft Windows BMP into PNG with transparency.
I will post a tutorial soon.
-~botalpha1 (aka lordalpha1)