meaning of "Windows Color System Defaults" in Vista "Color Managem

What is the meaning of "Windows Color System Defaults" in the upper part of
the Advanced Tab of Windows Vista "Color Management"?
I have a calibrated NEC monitorprofile and have no problems at all with
wrong colors or colorcast (colors look the same in Lightroom, Internet
Explorer en Windows Photo Gallery) ... but I don' t understand the "Windows
Color System Defaults"? Windows Help does not mention anything about the
upperpart of the "Advanced" tab and I searched all the calibrationsites
without succes.

At this moment, my settings are :
Default device Profile : sRGB IEC61966
Default viewing conditions profile : WCS profile for sRGB viewing conditions

What is the difference between "WCS profile for ICC viewing conditions" and
"WCS profile for sRGB viewing conditions" ?