Oh there is also a bold setting.

Maybe this is it.

I will re-do the list above and see if it makes a change:

Skybuck's Classic theme:

Active Title Bar 18 BOLD (off in aero theme)
Active Window Border 1 (default 4)
Border Pading 0
Caption Buttons 18
Icon 16
Icon Spacing (Horizontal) 80
Icon Spacing (Vertical) 48
Inactive Title Bar 18 BOLD (off in aero theme)
Inactive Window Border 1
Menu 18
Palette Title 15 BOLD (off in aero theme)
Scrollbar 16 (default 17)
Selected Items 18

So the classic theme has 3 bolds, the aero theme/blue theme has no bolds.

So this is not it... hmmm

Still wondering how to turn off bold text in windows explorer when aero theme is ON !

Bye for now,
Skybuck.