Problem recreating BCD on Windows 7 64bit - The requested system device cannot be found

Not directly related to your issue as you resolved it, but rather to your original description (particularly "The requested system device cannot be found." on BCD operations despite all attempts to recreate/rebuild):

This error can happen if you are booting from a USB stick, and your BIOS supports a given usb slot, but the windows PE/repair environment does not!

I spent two days pulling my hair out, wrestling with this issue (the BCD store was ALWAYS unavailable with this "The requested system device cannot be found." error, no matter what I did), only to find that the problem was simply the USB slot I was plugging my bootable USB stick in. By plugging it into a different (usb 2.0 instead of usb 3.0) slot, the standard repair actions worked fine.

To make matters worse, I later discovered that it was by plugging in the wrong slot and allowing the rescue environment to attempt auto-repair that I messed things up in the first place!

Update: Another user (improvedcomputers) contacted me to confirm that this also happened to them; as all their USB slots were unrecognized by Windows 7 PE they ended up having to pull the drive and perform the repair on another computer.

Update: I had hard time even reinstalling windows on my laptop. From this post I learned and realized the Windows 7 PE does not recognize USB drive. Although it booted from the USB drive image due to some reason it was not able to start up the installation process. After whole day of efforts finally I tried it with DVD and it worked. I am using Lenovo W520

Nothing from other answers helped in my case and I had no the ability to load the Windows RE from the DVD. Hopefully this answer trapped into my eyes.

I tried solutions from linked guides and finished with no BCD at all (actually I don't know if it was there in the start). So, the thing that saved me from reinstalling the whole system was:

bcdboot.exe C:\Windows /s C:

Hope it will help someone.

Update: This finally worked for me with one small modification. My issue was a combined problem of many listed here (booting from stick, screwing the initial working BOOT).

My problem was that RE registered my windows drive as D:\, while it was C:\ normally. Running bcdboot.exe D:\Windows /s C: did the trick!