I am trying to install the latest Ubuntu OS (16.04) on my old macbook 2007. The installer works fine until I get an error that says it is unable to install GRUB in /dev/sda . The guide I am following says to choose the option to "continue without the boot loader" , however the installer either freezes or crashes when I press okay. I am using a USB to install and am following this guide . Please help? I'd like to be able to use this laptop for school.