The Windows 7 "Photo Viewer" application uses only the matrix part and shows RGB shifted to GRB, while the Windows 7 file manager ("Explorer") uses the LUT part to colour manage its JPEG previews, so those are shown with correct colours, as do other applications that invoke/use the Windows CMM.
The Windows 7 explorer thumbnails definitely aren't using the display's associated profile. My guess is that they are colormanaged, but probably with a default internal destination profile (sRGB? On my wide-gamut TFT the thumbnails look overly saturated). Maybe Firefox is doing something similar, ie. silently defaulting to sRGB as destination profile if it can't cope with the display profile?
-- Florian Höch http://hoech.net