Is it true the display backlight does not flicker in XP or Vista?

I have the flickering backlight. It flickers when waking up from sleep, or from shutdown.. takes awhile to reach 'stable'. Touching the brightness slider in the system preferences will restore it back to maximum brightness, a few minutes later it may dim again slightly.

I have had a new motherboard, new inverter card. No change. And yes, I am up to date with all firmware, software updates, etc.

I have heard before that it is just OS X that flickers, but if you run Microsoft Windows on the Macbook it doesn't flicker anymore when waking up from sleep. Is this true?