Ok, I have no idea what I'm doing, and I'm a total newbie with the Ubuntu kernel and grub and whatnot. Right now, I have Ubuntu 13.04 installed on an external drive, and am trying to get it to boot on my laptop. Whenever I do it on my desktop, it works fine, but the laptop just brings up a grub 2 prompt. I googled for a while but came up with nothing at all. And, when I try to just type 'boot', it responds "error: you need to load the kernel first." any help is appreciated, bit if minimal techie speak is used, it would be even better!
So you did the installation on another computer and saved it to a external HDD, correct? I haven't done this before, and can't find much relating to your question. But have a read through here. It may answer your question because it sounded like the user was having Ubuntu issues as well.
Also from reading, you may have to reinstall due to GRUB2 issues. You can read the wiki documentation here.
But from what I can see just from looking around, there are a lot of issues wit installing Ubuntu on an external hard drive, and using it for multiple computers.