so I am dual-booting windows 8.1 and ubuntu 15.04 and for some reason GRUB2 stopped loading and it just goes straight to windows so i booted from the ubuntu live cd to reinstall grub2. i found the location of the partition with ubuntu which is /dev/sda5 so the commands i typed in was, "sudo mount /dev/sda5 /mnt" and then i type, "sudo grub-install --root-directory=/mnt /dev/sda" and with my desktop that works but it has a bios, my laptop doesn't. the error that it gives me is " grub-install: warning: this GPT partition label contains no BIOS Boot Partition; embedding won't be possible. grub-install: warning: Embedding is not possible. GRUB can only be installed in this setup by using blocklists. However, blocklists are UNRELIABLE and their use is discouraged.. grub-install: error: will not proceed with blocklists. "any help would be great! i've looked everywhere with no luck. thanks!
I figured out what to do.. Btw I have a Toshiba Satellite s55-b5280. All i did was go to change pc settings in Windows, then click update and recovery, then recovery, then under advanced startup, click restart now. After it restarts, a menu will pop up, i clicked "use a device" and then Ubuntu will be in that list, click Ubuntu and it'll restart and then the grub menu will show up. I just booted into Ubuntu and updated the system by typing sudo apt-get update && sudo apt-get dist-upgrade and waited (their were a decent amount of system updates) and now when i restated it, the grub menu shows up! I don't know if updating Ubuntu had anything to do with it but at least it worked.