Try with Boot Repair!
1 - Live CD
First, you'll need to boot from a Ubuntu Live CD.
2 - Install the Grub bootloader
To install the Grub bootloader, follow these steps.
Open Terminal from the Live CD, and run the following commands:
sudo add-apt-repository ppa:yannubuntu/boot-repair
sudo apt-get update
sudo apt-get install -y boot-repair
After a few seconds, Boot Repair's main window will open.
Reboot to test everything out.
If everything went well, you should be up and running now.
Once Ubuntu is loaded, you may open Terminal and issue the following command to automatically detect Windows and add it to Grub's menu, if it isn't there already.
Bootloader: a piece of code that runs before any operating system is running. A bootloader is used to boot other operating
systems. Each operating system usually has its own bootloader.
GRUB (Grand Unified Bootloader): a bootloader package developed to support multiple operating systems and allow the user to select among them during boot-up. It is Ubuntu's default bootloader.
Command, command line: the traditional Unix environment , where you type commands to tell the computer what to do.
Terminal: an application that allows you to access the command line. Open it by hitting its keyboard shortcut, Ctrl Alt T.