How can I install Ubuntu on my external hard drive?

[Portable]

I wanna install Ubuntu on my external usb hard drive. I want that Ubuntu only boots if my second drive is plugged in and that windows boots if my second hard drive isn't plugged in. I already had ubuntu installed but then Ubuntu and Windows only booted if my second drive was plugged in. That means I had to plug in my second hard drive every time I wanted to start windows or ubuntu. I fixed this problem, but now I have to reinstall ubuntu and i want it that ubuntu boots only with my second drive plugged in and that windows boots if my second drive isn't plugged in. Can someone help me?

 

[twindtrout9783]

First, go into your system's BIOS and set your USB's boot priority higher than your HDD. Then boot Windows and burn the Ubuntu Instalation Image to a DVD. I've never tried to install Unbuntu before, (I have installed Debian to one of my other computers) but it should allow you to set your external HDD as the drive for it to install to.