Reinstall GRUB Ubuntu 15.04

• Boot up Ubuntu 15.04 in live USB or live DVD
• Install and Run Boot-Repair

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

• select "Recommented repair" choice for fix grub

• Update grub

sudo update-grub

Additional for alter method

• for create boot cd or usb

• http://sourceforge.net/projects/boot-repair-cd/files/

Ref

• https://damayanthiherath.wordpress.com/2015/07/09/boot-repair-ftw-how-to-fix-the-broken-grub-with-windows-7-and-ubuntu-15-04/