Doing changes to my dual boot configuration

You can directly boot ISO from grub, but not exactly simple.
Newest versions I have to umount /mnt/ISO which uses sda partition, sometimes even the one I want to install. Some random mount??
This will boot an ISO from a hard drive or any second drive or flash drive
ISO Booting with Grub 2 from Hard drive - drs305
https://help.ubuntu.com/community/Grub2/ISOBoot
Examples - you may copy & edit for your path & ISO version
https://help.ubuntu.com/community/Gr...OBoot/Examples
http://ubuntuforums.org/showthread.php?t=1549847
UEFI grub install and example grub boot stanzas, Also Windows
https://wiki.archlinux.org/index.php...boot_USB_drive
Boot ISO from harddrive. To install it would have to be different partition

Generally easier to just create flash drive.

Tools for booting ISO
http://ubuntuforums.org/showthread.php?t=2289225
Not ISO boot, uses syslinux - sudodus

One pendrive for all PC (Intel/AMD) computers

http://ubuntuforums.org/showthread.php?t=2259682
UEFI & BIOS & Live installer - sudodus
http://ubuntuforums.org/showthread.p...0#post13468260
http://ubuntuforums.org/showthread.p...6#post13262506

While old XP required IDE, better to use AHCI. Required if a newer SSD.

If during install it does not find Windows, run this:
sudo update-grub

With multiple drives either use Something Else or totally discoect all but Ubuntu drive when installing. Something Else is the only install option that gives you the choice on which drive to install Ubuntu and you want it on same drive as Ubuntu install. Default is always sda.

Any install with Something Else which is required with exteal drives or any second drive or any install with separate /home
Also shows combo box with location of grub2 boot loader
https://help.ubuntu.com/community/Grub2/Installing
Does not hightlight changing boot loader to sdb, if exteal drive, but shows other install screenshots:
http://askubuntu.com/questions/31278...in-a-dual-boot
http://askubuntu.com/questions/27437...p-boot-optiond
Install 14.04 Something Else explanation and screenshots (note boot load to VM, most may install to MBR of drive sda, or sdb)
http://www.tecmint.com/ubuntu-14-04-installation-guide/
And you want this screen to choose where to install the grub2 boot loader which is only available with Something Else or manual install
https://help.ubuntu.com/community/Gr...ing_Else.22.29: