Test this:
Start up your computer with the USB or DVD Windows 8 recovery media in the system.
When the computer boots off the recovery media, pick the Troubleshoot option.
Then choose Advanced Options.
and head on over to the Command Prompt.
The computer should reboot and then ask you for the account.
Click your account to continue.
Then login to get started.
We’re going to use the built in partitioning tool called diskpart to confirm that:
We have all the right partitions
EFI partition is formatted correctly.
In the black screen that looks like a dark abyss, type:
diskpart
and enter this command:
sel disk 0
Now that the first disk is selected we need to view all the partitions
list vol
Verify that the EFI partition is using the FAT32 file system then select the volume and assign a drive letter to it.
Let’s say your EFI partition is on Volume 3, the next thing you would type is:
sel vol 3
Then assign an arbitrary drive letter to the parition. Let’s use v.
assign letter=v:
You should see a message saying: DiskPart successfully assigned the drive letter or mount point.
Exit the diskpart tool by typing:
exit
You should still be in the command prompt but outside of the DISKPART> prompt.
We need to repair the boot record. We can pull that off like so:
cd /d v:\EFI\Microsoft\Boot\
bootrec /fixboot
The CD command tells the command line interpreter to change the directory to the volume label that has the EFI boot record.
Then the bootrec /fixboot command attempts to repair the selected volume.
Now we need to recreate the Boot Configuration Data (BCD) store, so let’s backup the existing store first
Type:
ren BCD BCD.old
Now that we backed it up, let’s recreate the BCD store:
bcdboot c:\Windows /l en-us /s v: /f ALL
Now remove the recovery media and reboot and you should be all set.
Source: windows.microsoft.com/en-us/windows-8/system-recovery-overview
