Fix Windows 8 bootloader after converting MBR disc to GPT

Question

I bought a new MoBo, processor, and some 3TB HDDs last week and am currently setting up a clean installation of Windows 8 on the machine.

The MoBo is an Asus RoG Maximus VII Ranger (What?! It was decently-priced. And shiny. o.o) with the on-board Intel Rapid Storage Tech semi-hardware-RAID thingy. I've configured a RAID5 array with three of the 3TB disks (I'm already aware that a three-disk array with large drives isn't ideal, but I plan to rectify that later by expanding the array).

Windows 8 installed successfully on the resulting 5.4TB array (on the third attempt… >:/) using an MBR partitioning table. Once the machine was running and I'd installed all the hardware drivers for networking, etc, on it, I used AOMEI Partition Assistant to convert the disk to use GPT. This succeeded, and upon rebooting the UEFI bootloader throws an error complaining that a required device is missing, which I expected.

I'm currently booted to the Windows 8 Install DVD in order to fix the problem. After loading the IRST RAID driver, I used diskpart to list the volumes on disk 0, which correctly showed the 350MB boot partition created by the installer, and my 5.4TB C:\ partition.

When I run bootrec /scanos, it gives the following output:

Successfully scanned Windows installations.
Total identified Windows installations: 1
[1] C:\Windows
The operation completed successfully.

However, when I run bootrec /fixboot, I receive this error:

The system cannot find the path specified.

I get the same error from bootrec /rebuildbcd.

What am I doing wrong?

Answer 1

You need to split the 350MB MBR boot partition into the System and Reserved partitions used by the Windows GPT boot system.

Based on instructions I wrote last time I did this process:

Load a command prompt from the DVD (Repair Your Computer -> Troubleshoot -> Advanced options -> Command prompt)

diskpart
select disk 0
list partition # To verify layout
   Partition ###  Type              Size     Offset
   -------------  ----------------  -------  -------
   Partition 1    Primary            350 MB  1024 KB
   Partition 2    Primary            126 GB   350 MB
select partition 2
assign letter=C
select partition 1
delete partition
create partition EFI size=100 offset=1
format quick fs=fat32 label="System"
assign letter=S
create partition msr size=128 offset=103424
list partition
    Partition ###  Type              Size     Offset
    -------------  ----------------  -------  -------
    Partition 1    System             100 MB  1024 KB
    Partition 3    Reserved           128 MB   101 MB
    Partition 2    Primary            126 GB   350 MB
exit
bcdboot c:\windows /s s: /f UEFI

Now reboot. Hit the BIOS and enable UEFI booting. Hopefully Windows will now load.