# Ubuntu – Dual Boot Win8.1-Ubuntu 14.04 – Cannot load Win8.1 after reinstalling Ubuntu

14.04boot-repairdual-bootuefiwindows 8

As suggested by the title of the topic I'm having troubles with the dual boot of Win8.1 and Ubuntu 14.04…..forgive me if the post is gonna be a little long, but I guess it should be better to explain how I got into the current situation, please take the trouble to read through the end of it.

So, my laptop (it is a Dell Inspiron 17 5748) had Windows 8.1 as the default OS, but I needed to install Ubuntu.
I followed some guides on the UEFI installation, making a manual partitioning of the disk, and I ended up with a dual boot working perfectly fine (at boot, a GRUB screen would appear asking me which OS I wanted to boot).

Now, I was with a professor who was helping me to compile the programs I need to use….long story short, she mistakenly removed a system folder, so that Ubuntu couldn't load anymore. Windows was still working, of course.

No big deal, I got back home and I prepared to install Ubuntu again.
But this time, I made a mistake myself. During the process, the system detected the previous installation of Ubuntu, so this time I didn't use the manual partitioning, but I selected the option to reinstall the OS.
I thought it would only reinstall Ubuntu, leaving the Windows partition alone, but instead it formatted everything and installed Ubuntu as the only OS.

After barely restrainin myself from throwing the PC out of the window, I created an empty partition and installed Windows in it.

After the installation, the system booted Windows by default (no GRUB screen), which I guess is normal…..I loaded Ubuntu from the BIOS, and I used Boot Repair to solve it.
It gave me this error

so I selected the Advanced Options, I activated the option "Separate /boot/efi partition" selecting the sda1 partition, and I launched it.

Now, when I turn on the PC the GRUB screen appears, showing the options to load Ubuntu or WIndows.
When I choose Ubuntu it works fine, but if I select Windows an error flashes for an instant, saying

Failed to open \EFI\Microsoft\grubx64.efi - 800000000000000E
Failed to open \EFI\Microsoft\MckManager.efi - 00000000000000000E


and it goes back to the GRUB screen.

I created a Boot Repair log if it can be of any help: http://paste.ubuntu.com/10290244

Any ideas to solve this and load Windows again?

Thank you!

P.S. Sorry for the bad English, if I wasn't clear enough just tell me!

• After barely restrainin myself from throwing the PC out of the window, I created an empty partition and installed Windows in it.

So you had an EFI installation of Windows at/after this point? If your answer is yes, then that was good, and we can start troubleshooting from here.

After the installation, the system booted Windows by default (no GRUB screen), which I guess is normal.....

Good. Yes, that is how it should be.

I loaded Ubuntu from the BIOS, and I used Boot Repair to solve it. It gave me this error

Start again at installing Windows (alternative: reinstall the Windows bootloader with bcdboot), but this time don't use boot-repair. It generated another issue that we don't want in this situation (replacing what the default setup of GRUB thinks is the Windows bootloader file, which boot-repair unfortunately modified), instead we want the initial problem solved.

What is your actual problem with installing and booting Ubuntu on this computer alongside Windows?

I was able to boot Ubuntu on every UEFI-capable machine I got my hands on so far without additional tools. (I'm not bragging here.) It just comes down to understanding the boot behavior of the firmware in your computer and running grub-install with the right parameters, not modifying the Windows' boot setup. Some firmwares only allow to boot from the default bootloader, in that case try the answer from Is it still possible to install Ubuntu to an external harddrive with UEFI?