Z61t keeps insisting on lower res on external panel

[bradtem]

Having a baffling problem with a z61t with intel graphics chip and WinXPSP3.

First hooked it up to a nice HP external monitor that is 1920x1200. While if you go into the monitor properties it says that the monitor has reported available modes including 1920x1200 and 1920x1080, the thinkpad's windows settings slider and intel graphics control panel only permit 1650x900. This works but is of course wasteful and slightly fuzzy.

So we go out and get an Acer 20" monitor that is native at 1600x900. And lo, even though the plug and play monitor properties shows that this is one of the available modes, all that can be selected is 1600x1200 or 1280x800 (which is also the res of the panel inside the laptop.) So again, it's only letting us do one resolution lower.

The intel graphics driver appears to be the newest. So what gives? Why is the display driver not paying attention to the EDID data we know is loading, and refusing to display the proper size, and offering a general set that is smaller instead?