How to run installed Windows 8 along Ubuntu, after installing Ubuntu in Legacy mode?

I have a Lenovo Ideapad with pre-installed Windows 8.1 In order to install Ubuntu I disabled secure boot and changed boot mode from UEFI to Legacy. This allowed me to install Ubuntu and the grub loader is also showing an option to either boot into Windows or Ubuntu, but whenever I try booting to Windows it says Cannot load.

This happens because the boot order is set to Legacy mode and Windows 8 will boot only with UEFI. I am unable to access my BIOS from where I can change the boot order. I press F1/F2 on booting but it doesn't load the BIOS, and directly goes to the grub loader screen.

How can I make my Windows 8 run along with Ubuntu?

You need to convert your Ubuntu install into EFI mode.

1. get a 64 -bit Ubuntu disk if you don't have yet
2. set your BIOS (UEFI firmware) so that it boots USB/DVD in EFI mode
3. boot onto your 64bit Ubuntu disk, choose Try Ubuntu
4. connect internet, install Boot-Repair this way and use it that way in order to convert your Ubuntu install into UEFI mode.

The key for BIOS might be Fn+F2 in case of new laptops.

Boot into Ubuntu and install boot-repair

sudo add-apt-repository ppa:yannubuntu/boot-repair
sudo apt-get update
sudo apt-get install -y boot-repair

Now launch boot repair from either :

1. the Dash (the Ubuntu logo at the top-left of the screen)
2. or System->Administration->Boot-Repair menu (Ubuntu 10.04 only)
3. or by typing boot-repair in a terminal

Then click the "Recommended repair" button. When repair is finished, note the URL (paste.ubuntu.com/XXXXX) that appeared on a paper, then reboot and check if you recovered access to your OSs.

This will install the grub-efi bootloader. Follow the on-screen instructions given by boot-repair to complete the installation.

Now reboot your system and turn on EFI mode in BIOS. You will able to boot into both Ubuntu and Windows in EFI mode itself. The secure boot option in BIOS needs to be disabled.