tried to reinstall 15.10 from cd

[Ezra Lee]

And then grub could be installed

ProblemType: Bug
DistroRelease: Ubuntu 15.10
Package: ubiquity 2.21.37 [modified: lib/partman/automatically_partition/question]
ProcVersionSignature: Ubuntu 4.2.0-16.19-generic 4.2.3
Uname: Linux 4.2.0-16-generic x86_64
ApportVersion: 2.19.1-0ubuntu3
Architecture: amd64
CasperVersion: 1.365
Date: Thu Jan 21 10:24:07 2016
InstallCmdLine: file=/cdrom/preseed/ubuntu.seed boot=casper initrd=/casper/initrd.lz quiet splash --- maybe-ubiquity
LiveMediaBuild: Ubuntu 15.10 "Wily Werewolf" - Release amd64 (20151021)
ProcEnviron:
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
SourcePackage: grub-installer
UpgradeStatus: No upgrade log present (probably fresh install)

[Phillip Susi (psusi)]

Your disk is partitioned with GPT but you are in a bios booting machine. This requires you to create a 1 mb bios_grub partition on the disk, or switch back to the dos partition table.