How to choose what to boot?

[Gadman]

How do I install Ubuntu so that I can boot it or my windows at start up? Thanks for the help!

Edit: Actually, how would I install it to my portable hard drive and be able to load it up from there?

[natirips]

If you wish to install it on your portable/external HDD or even USB stick (I recommend at least 4GB because my 2GB stick proved not to be enough), but load it on only one computer (the one you're installing from), simply treat the external drive as internal (ignore the fact that it is external) and install normally. Just make sure you install GRUB onto that device (not on your intenal drive). Edit: check your BIOS for boot order when booting from your external drive.

If you want to install on external drive in order to be able to boot on any computer see: http://www.pendrivelinux.com/ and scroll down a little. It has the list of various Linux distribution (including Ubuntu) that can be installed onto external drives/USB sticks and the corresponding howtos.