Datacolor User to User Support Group.

Thanks for the replies.

The monitors are identical Dell LCD monitors connected via DVI to a
dual DVI Nvidia Geforce AGP videocard. I am able to calibrate both,
but they remain somewhat different. They are positioned side by side
against dimly lit white wall, the light is coming from the right side
and is fairly dim most of the day. The light does not directly hit the
monitors. Windows XP Pro SP2.

I wasn't targeting luminance values.

One of the monitors is also connected via VGA to another computer with
a Matrox G400 Max card, but I haven't attempted calibrating it yet.