installing on intern al HD, but bootable from external

[Iacopo Volpi]

failure to install grub on the external HD (which was recognized)

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: ubiquity 2.10.20
ProcVersionSignature: Ubuntu 3.2.0-34.53-generic-pae 3.2.33
Uname: Linux 3.2.0-34-generic-pae i686
ApportVersion: 2.0.1-0ubuntu15
Architecture: i386
CasperVersion: 1.315
Date: Tue Dec 11 23:16:18 2012
InstallCmdLine: noprompt cdrom-detect/try-usb=true persistent file=/cdrom/preseed/ubuntu.seed boot=casper initrd=/casper/initrd.lz quiet splash -- maybe-ubiquity
LiveMediaBuild: Ubuntu 12.04.1 LTS "Precise Pangolin" - Release i386 (20120817.3)
MarkForUpload: True
ProcEnviron:
 TERM=unknown
 PATH=(custom, no user)
 LANG=it_IT.UTF-8
 SHELL=/bin/bash
SourcePackage: grub-installer
UpgradeStatus: No upgrade log present (probably fresh install)