Your Windows seems to be installed in efi mode. To get a dualboot, you have to boot the installer also in efi mode.
** Changed in: grub-installer (Ubuntu) Status: New => Incomplete -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1675826 Title: It was not possible to install a bootloader at specified position. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/grub-installer/+bug/1675826/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs