I was wondering how do I re-install Windows Vista from an external hard drive. I am using an HP pavilion dv5 laptop.
You cannot just boot from an external drive (any drive, cd, hard drive, flash drive etc) without setting it up as a boot drive. When you burn a ISO image of VISTA/XP the ISO image has been setup to allow booting from that drive. When you simply copy something from one place to another, it doesnt mean that its going to boot.
But I've seen this done, you can setup an external drive to make it an installer, but the bios must support booting from a external drive.
With all that said, take a look here: http://wintoflash.com/home/en/