Windows 8 boot loader corrupted

Problem: 

 Installed Windows 7 and Windows 8 in EFI mode on a hard disk some days past. Today, the boot loader is absent or corrupted.

At present have the Windows 8 installer on a flash drive and tried using the Automatic Repair option to repair the boot loader but it didn't do anything. The Startup Repair option is also absent in the Windows 8 installer.

How I can repair or recreate the EFI boot loader from the Command Prompt?

BCDEDIT returns the following message:

The requested system device cannot be found.

Solution:

Firstly, boot from a UEFI Windows 8 recovery disk (CD/DVD/USB) - I found that the automated recovery process didn't find the correct Windows partition, nor when I managed to add it to BCD settings would it make it reliably boot-able e.g. using BCDEDIT I got it to find and launch the Windows partition but it refused to cold boot or would not "keep" the settings after a 2nd reboot or power off.

Go into the Advanced options and run the Command Prompt.

Use DISKPART tool to ensure you have all the right partitions - key thing here is your EFI partition being FAT32

DISKPART> sel disk 0

Disk 0 is now the selected disk.

DISKPART> list vol

  Volume ###  Ltr  Label        Fs     Type        Size     Status     Info
  ----------  ---  -----------  -----  ----------  -------  ---------  --------
  Volume 0     E                       DVD-ROM         0 B  No Media
  Volume 1     C                NTFS   Partition    195 GB  Healthy    Boot
  Volume 2         WINRE        NTFS   Partition    400 MB  Healthy    Hidden
  Volume 3                      FAT32  Partition    260 MB  Healthy    System

I then assigned a drive letter to the EFI partition

DISKPART> sel vol 3

Volume 3 is the selected volume.

DISKPART> assign letter=b:

DiskPart successfully assigned the drive letter or mount point.

Exit Disk-part tool and at the command prompt run the following -

cd /d b:\EFI\Microsoft\Boot\

bootrec /fixboot

Delete or rename the BCD file

ren BCD BCD.bak

Use bcdboot.exe to recreate BCD store

bcdboot c:\Windows /l en-gb /s b: /f ALL

The /f ALL parameter updates the BIOS settings including UEFI firmware/NVRAM, /l en-gb is to localise for UK/GB locale, it will default to US English

Reboot and cross your fingers.

This gave me headaches. I was going in circles for a long while and there isn't a lot of reliable info about fixing UEFI/Windows 8 at the time of writing

[EDIT]

To re-enable Hyper-V, I also had to run the following -

bcdedit /set {default} hypervisorlaunchtype Auto
bcdedit /set {default} nx OptIn

CHEERS !!!