Sunday, June 3, 2018

Notes on Repairing/Recreate Windows 10 EFI Bootloader without Reinstallation

For whatever reason, my windows installation has its bootloader on a different drive. i.e., say the windows 10 is on disk 1, but its bootloader is on disk 0. The computer has to access disk 0 in order to have disk 1's OS running.

Unfortunately,  my boot drive is finally dead yesterday, so I was unable to boot up despite the OS itself being good.

Here are few steps I did:

  1. remove the dead disk 0. (with disk 0 connect, my BIOS would stuck at POST)
  2. boot into ubuntu live CD, use GParted to move the OS partition and make a room of 500MiB before it
  3. Create the EFI partition. it is just a FAT32 partition with boot label. 
  4. use a windows 10 installation media, hit shift+F10 to enter cmd, then use 
    "bootrec /RebuildBcd"

    to create the bootloader
  5. For whatever reason, now I can see the bootloader, but it somehow won't get me into windows 10. So now I used the windows 10 installation media's repair tool, and it automatically repaired it. (note I tried using this step before everything else, but it won't work until I create the EFI partition manually)
  6. Done