The one in this location?
Vista Legacy > Start Menu > Basic > PlacesList
Start Menu > Panels > Basic > PlacesList
Start Menu > Panels > Basic > Logoff
AlphaThreshold:
You can set the transparency value to be used as a threshold by entering a value between 0 and 255 in the box. All transparency values above this threshold will become opaque and all transparency values below or equal to this threshold will become completely transparent.