It was not possible to install a bootloader at specified position.

[Arkadiusz Szymon Mielwski]

During installing Ubuntu I needed to select a partition to install it by my own because Ubuntu didn't see my Windows 10 installed. At the the end of installation I got an error that is impossible to install bootloader at specified position.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: ubiquity 2.21.63.3 [modified: lib/partman/automatically_partition/question]
ProcVersionSignature: Ubuntu 4.8.0-36.36~16.04.1-generic 4.8.11
Uname: Linux 4.8.0-36-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.5
Architecture: amd64
CasperVersion: 1.376.2
Date: Fri Mar 24 16:44:14 2017
InstallCmdLine: file=/cdrom/preseed/ubuntu.seed boot=casper initrd=/casper/initrd.lz quiet splash --- maybe-ubiquity
LiveMediaBuild: Ubuntu 16.04.2 LTS "Xenial Xerus" - Release amd64 (20170215.2)
ProcEnviron:
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: grub-installer
UpgradeStatus: No upgrade log present (probably fresh install)

[apt-ghetto (apt-ghetto)]

Your Windows seems to be installed in efi mode. To get a dualboot, you have to boot the installer also in efi mode.

[Launchpad Janitor (janitor)]

[Expired for grub-installer (Ubuntu) because there has been no activity for 60 days.]