I am having this problem.
New computer, new mobo DG43NB. In the beginning, I used the onboard video. Later, I installed a PCI Express card, NVidia GT 9400. No problems for 1 year, never got a BSOD with Windows 7 Ultimate. Suddenly, I started getting BSODs, without any changes to the PC, and I managed to find the culprit: igdkmd64.sys. (in Safe Mode, computer locks at this driver, plus other information from the BSOD). This driver is in folder Windows\system32\drivers. In Google, I found no solution, except that there are too many people with the same problem with that driver (from Intel onboard graphics) and I only found, as useful, the recommendation to update the driver.
1. If I have a dedicated PCI express card installed, and automatically the mobo disables the onboard graphics, why, then, igdkmd64.sys loads (and locks Windows with a BSOD) ? It shouldn't load at all, that's what I supposed. The onboard graphics should be disabled automatically... It should only load if I removed the dedicated PCI Express. The driver version is May 2009. If I am correct, then I have a bug. I tried in the BIOS, for the graphics: Auto, PCIe first, no solution. After several trials, I manage to boot. It's a random thing, however frequent.
2. I downloaded the latest Intel graphics but it doesn't install - I get an error message like this "version incorrect" or "operating system incorrect", something similar. I downloaded the correct graphics - for Win 7 64 Ultimate, I am sure, from the Intel site, for my mobo. New version is 2010. The explanation can only be, I suppose: I am running the NVidia drivers for the dedicated card, then, the downloaded Intel driver does not install. I am supposing that's a correct behavior.
3. Then, I am thinking that I'll have to uninstall the NVidia drivers and physically uninstall the dedicated card and plug my monitor on the onboard VGA terminal. Then, I'll boot with the onboard Intel graphics. Then, I'll be able to install the new version I downloaded. Then, I'll begin all over, installing the dedicated card again from scratch.
4. I also thought in finding a way to rename igdkmd64.sys to igdkmd64.old so that Windows won't find it. Don't know if this is possible...
I then ask you, please, if you have had similar problems, if my assumptions are correct, that is:
a) onboard graphics should be automatically disabled, then Windows loading igdkmd64.sys when I have a dedicated card is a bug or a defect of my mobo;
b) I can't install the Intel update because I am using the dedicated card;
c) If the procedure I devise to resolve the issue is correct (uninstalling the dedicated card first), or if you have better suggestions or solutions.
Google "igdkmd64.sys BSOD Windows 7" and you'll find lots of links. No solutions.