Dual boot Windows 8.1+Ubuntu12.04 - can't boot on windows

Question

I got a Toshiba Sattelite S70-b-110, with windows 8.1 pre-installed. I partitioned my HDD into 4 : C:/ (Windows install) ; P:/ (Windows Data and installed programs) ; Ubuntu install (/) ; Ubuntu swap ;

I had installed Ubuntu 14.04 and everything was great! However, i needed 12.04 to run some programs, and I decided to uninstall Ubuntu the wrong way: I booted on Windows and deleted the ubuntu partition. Result: PC didnt load grub, and I couldn't boot.

I managed to bypass the situation and formatted my PC factory new, with Windows 8.1.

Then i partitioned the disk again, and went for Ubuntu 12.04. Installation was successful, but my grub didn't show Windows 8, and automatically booted on Ubuntu. Then i went online to search for answers, and I completely ruined the situation..

I followed this question, and I tried changing /etc/grub.d/30_windows and /etc/grub.d/40_custom , nothing worked.

Then i tried to run Ubuntu through USB and boot-repair , and then everything went crazy. I got "Invalid arch independent ELF magic" , and then I ran Ubuntu again from USB and used:

sudo mount /dev/sda7 /mnt; sudo grub-install --boot-directory=/mnt /dev/sda

After I rebooted, I could see Windows Boot UEFI Loader but when I tried to boot I got an error: "invalid signature". I could boot on Ubuntu though.

I'm now asking for help on this matter. I want to be able to boot on both Ubuntu 12.04 (which I already can) and Windows 8.1.

Additional info: http://paste.ubuntu.com/8547720/

Sorry for possible double entries, but I really want to make sure that I don't ruin my windows partition, since I forgot to backup my files and I really need them.

Thanks in advance,

Pedro Marques

Answer 1

It seems you have mixed BIOS and UEFI booting.

1. Windows seems to be installed in UEFI mode (only 64-bit Windows can be installed in UEFI mode)
2. Disk is in GPT style (has EFI system partition + MS Reserved)
3. Linux is installed using MBR booting (disk has special BIOS/MBR booting partition)

===============================

Easiest solution:

1. delete BIOS boot partition (sda9)
2. Fix Windows booting using Windows Recovery/Installation media (boot to recovery console and type "bcdboot Z:\windows" where Z: is your Windows drive, change drive letter accordingly - on Z: you should have \windows directory)
3. Reinstall Ubuntu 12.04 in UEFI mode !!!

To install in UEFI mode you boot in UEFI mode - select DVD UEFI boot or USB UEFI boot !!!

Check also "rEFInd" boot manager used for multi-booting Windows/Linux. Can be installed later as a software boot switch.

Check also BootNext tool - allows direct booting of Linux/Ubuntu from Windows.