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I've got a Dell E6400 laptop with Intel GMA 4500MHD integrated video driver running WinXP SP3 with the basic Dell dock, which has a DisplayPort and a DVI output.

  • The DisplayPort output is hooked up to a 2560x1600 Dell 30" monitor (via a DP to duallink DVI converter, but I don't think that is relevant).
  • The DVI output is hooked up to a Dell 20" 1600x1200 monitor.

Everything used to work fine. I'd go into standby, eject the laptop, and the laptop screen worked fine. When I'd redock it (with the lid closed), I could press the power button, and both external monitors would come on, at the right resolution, position, etc. This worked fine for months = hundreds of undocks/docks.

I went on vacation for a week, using my laptop off and on as I normally would (I wasn't messing with the graphics/drivers/etc - it was only email), and when I came back, the external monitors didn't display anything when the laptop was docked with the lid closed and I pressed the power button. The power button on the 30" did change from green (or yellow or something - I'm colorblind) to blue, indicating it was seeing a signal from the laptop, but the screen stayed black.

I finally found that if I opened the lid of the laptop I could get an image to display on the 30" - basically it's acting as if the 30" was an external monitor connected to an undocked laptop - pressing Fn F8 cycles through laptop-only, laptop+30", and 30"-only screens.

So I'm assuming some setting somewhere got hosed, but I haven't been able to change the behavior back (or at all) using XP's Display Properties or Intel's display utility.

Does anyone know where the display info is stored so I could examine it and/or reset it?

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What does Windows say your current hardware profile is? Sometimes Windows XP is acting strange in this regard, adding new profiles for the same hardware for no visible reason, using a wrong one etc. It seems that in your case it's using an undocked profile while being docked. You might get things working again by deleting all the hardware profiles and rebooting to force Windows to create new ones based on what it finds.

Is it possible that somehow the sensor of your display lid got disabled? Maybe the notebook can't realize that the lid is actually closed -- Dell machines can only power two displays at a time, so with the lid display enabled you disable one of the external ones. Some displays use a little pin that is pressed down into the notebook chassis. It may be possible to accidentally break it off -- then the display won't know if it is opened or closed. Other machines use a light sensor -- a malfunction here might be fixed with some dark paper put over it.

Did you warm- or hot-dock? XP may be quite sensible about docking at times, especially when you're using a lot of externally connected hardware. I've made it a habit to always power down and reboot if I need to change the docking status.

Have you made absolutely sure some colleague hasn't messed with your cables? I mean, as in pull each plug, examine both the plug and its receptor and re-plugging it, and following each of the cables to ensure nothing is broken?

The combination of Windows XP and Dell E-Class points me to think that you're a corporate user who has no choice but to using this exact setup. Otherwise you might consider upgrading to Windows 7 which operates a lot smoother in the docking business. It can't do miracles with regards to unplugged cables or damaged lid sensors, though.

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First, great job on the Sherlock Holmesian conclusion that I'm a corporate user who has no choice but to using this exact setup - spot on! I just have one profile that's pretty plain vanilla - it doesn't even seem to recognize that there is a dock ("Dock ID: Unavailable"). I tried tweaking a few settings (checking "This is a portable computer" and changing the docking state) and rebooting; no effect. I think the profile seems to be basically ignored. Lid switch definitely works - opening the lid is how I get the 30" to display. Cables are fine. Warm (in suspend) (un)docking. Thx anyway! –  Fred Hamilton Sep 1 '10 at 17:26
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