Thanks for the input. You grub is installed but it couldn't find the linux location.
The reason could be you installed linux in your external hard disk which may have different name at time of boot and at time of installation.
So it would be better to do the following way,
Install grub & linux at secondary disk.
Boot from secondary disk.
Now, You follow the below procedure.
- Take XP cd, boot into recovery mode. Use
fixboot, fixmbr commands to delete GRUB. You can google for more information.
- Plug in the external hard disk.
- Boot using the live usb/cd you used for installation earlier.
Open dash, search for disks, open it, identify the external disk name. Refer the picture below

Connect to internet, install boot-repair tool using following commands
sudo add-apt-repository ppa:yannubuntu/boot-repair && sudo apt-get update
sudo apt-get install -y boot-repair && boot-repair
- Choose
Advanced options
- Go to
Grub location. Refer the image below

- Choose
Place GRUB into, and select the device name from dropdown. External device name will be same as you identified in step 4.(it likely to be sdb, please verify)
- Then click on apply.
- On reboot, open BIOS and change the boot order. External disk should be on top of internal disk so that ubuntu can load.
I personally don't have experience in using external disk as ubuntu boot medium, if there are any easier method, let me know