NVIDIA drivers upgrade crashed my Windows 7 installation, so I'm working to undo the damage.

What I can do: I can boot Windows install from the USB drive, and I can boot the Hiren's Boot CD. Although automated Windows repair fails, I can get to command prompt when I boot Windows install from USB drive, and I can see my drive and all my data.

What I cannot do: I cannot boot into Windows - I get this message:

Windows failed to start. A recent hardwware or software change might be the cause. To fix the problem:
1.insert windos cd and run a repair your computer option.
File: /boot/bcd
Status: 0xc000000f
Info: an error occured while attempting to read the boot configuration data.

It seems that something is wrong with my /Boot/BCD, so I'm trying to recreate it from scratch. I've tried all the methods detailed here (including Windows repair which fails), and I'm left with the last one (near the bottom of that page). When I type the following command as in the tutorial:

bcdedit.exe /import c:\boot\bcd.temp

...it fails with the following error:

The store import operation has failed.
The requested system device cannot be found.

Many Google results say that I must use diskpart to set my partition active, however it's already set as active.

Also, when I try this:

bcdedit /enum

It fails with similar message:

The boot configuration data store could not be opened.
The requested system device cannot be found.

Does anyone know what does that error message mean, and what is the requested system device?

I'd like to avoid having to reinstall Windows since all the files on disk seem to be fine.