How to install Ubuntu11 in external Hard drive

Hi Guys..
I want to install Linux on my portable hard drive.
I created a 20GB partition in my hard drive for linux, Now I want to make it bootable mean when I connect it to system n start the system it will start the LINUX and when start without usb-hard drive it should start the windows.

Thanks for help and suggestion guys..
Atul Singh

Check Boot and run Linux from a USB flash memory stick | USB Pen Drive Linux, this is for Ubuntu 10.04.

Hi Buddy,
I am not want to boot it from USB as a LIVE OS , I want to install it on my portable hard disk partition.
Thanks for your suggestion

OK,
I did something like this some time ago, I had the standard dual boot menu and one of the operating systems was installed on an external drive.

If you don't want to have the dual boot menu, you should try to install grub on the external drive, I suppose, and you should move the external drive up in the boot order.