dual boot - grub2 installation fails for Ubuntu 16.04 LTS

I have been trying to install Ubuntu 16.04 on my Lenovo Ideapad500-15isk alongside windows 7 using a usb live disc.

I have kept 8200MB of swap space

and 20482MB of mount point /

and around 390 GB of space with mount point /home.

I downloaded the 64 bit ISO file from http://releases.ubuntu.com/16.04/ and used rufus as well as the Startup disc creator in Ubuntu to create the live disc.

But the Ubuntu Installation fails to load grub 2 every time. What could have possibly gone wrong?

Also since I'm already using a 64bit windowsi doubt that is the problem.