To start off I'll let you all know I have a Lenovo T430s running the preinstalled windows 8.1. What my initial plan was (and I have yet to find a way to do it), was to install Ubuntu 14.01 onto an external hard drive I have (USB3.0, pulled it out of my old Toshiba laptop and put it in one of those cases you can buy so it has a usb hookup) so I can run Ubuntu when I have the hdd hooked up but doesnt affect my internal hdd at all. I've found some tutorials that get me close but nothing that works. If anyone has done this it would be very helpful if you post a tutorial you followed or tell me what steps you took. I don't want to make this initial post too long so I'll leave it at that, please ask for more detail if you want it. Any help is appreciated, thanks!
UEFI is often on Windows 8.1 pre-installed laptops, and it tends to make a lot of things more complicated, and some settings may need to be changed to get anything different to boot.
If a live cd/dvd/usb just boots without any fiddling then you may be in luck & your external HD may just boot too after it has Ubuntu installed.
And installing Ubuntu to the external drive while the internal drive is unplugged could give you 100% assurance that nothing on your internal drive will be changed. Sometimes, rarely, the wrong drive is installed to or overwritten by mistake or by bug. Since you're installing to a completely separate drive it's easy insurance to protect your internal drive.
Or using another computer to install Ubuntu to the external drive might work too...