What's your source for the driver? If it's not on a CD, you may need to redownload to verify its integrity.
Also, you mentioned the bootsector was corrupted. Did you reformat the drive completely?
I honestly have no "real" suggestions for you, so I just thought I'd cover some basics.
The drivers were downloaded from intel.com, and I've tried on two different internal HDDs...
No one I've talked to at work in our IT department has any idea, either. At this point I may just try a stand-alone NIC to see if I can at least get online, patch up the OS, install the latest motherboard drivers, etc. and then try to get the onboard NIC working again.
I have the same issue. I have a D965WH Board, I'm using it as a File Server. I just shut it down last night to install new HDDs and it would shut my PC down during Windows Boot. So I installed a fresh copy of the OS on another Drive, and as soon as it is about to finish installing the OnBoard NIC GB Driver it would Turn Off / cause my PC to instantly shut off. I have tried updating the BIOS, I'm using the lastest drivers, nothing. Any Ideas? Were you able to figure out what was worng with yours, my issue may be very similar. My guess is the OnBoard NIC went bad.