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 load image Failed to open \EFI\Microsoft\MckManager.efi - 00000000000000000E Failed to load image
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?
P.S. Sorry for the bad English, if I wasn't clear enough just tell me!