Well, the smartest and quickest thing to do, is to burn that iso to a DVD, and boot the machine BEFORE you put in any HDD. You can't use an iso that's on a pen drive. It has to be burned to a DVD, to extract and become bootable.
Then, after the boot completes, instead plug in an external HD, then run the install with the external HD as the target, so you can first see if you'll like it. Most Linux distributions work on almost any PC configuration, so long as the RAM is at least 1 GB. I have 19 Windows machines and run Linux on all of them.. externally. None of the internal hard drives have or need Linux installed. That way, I can plug the Linux into any of my machines from Atom to Xeon to i7 quad. And, if ever Windows borks, it won't even matter if the MBR is messed up. No grub to deal with. So my Linux cannot be messed up by some other OS nor do I need to operate it solo on an internal drive.
So the only issue is what size external drive. Same issue as internal. With all the same effects and results, except some external drives are slower. Depends on what kind you use.
So the 'step by step' is that of the distro's installer program, which it then gives you. Generically, the installer wants you to tell it WHERE to install, then getting it to configure the partitions on that (EXTERNAL) drive for you -- most installers I've encountered, go buggy if you try to configure the partitions yourself -- then it asks you for domain/network name, user name as first root, password. Some distros want to be connected to the internet when you do this, some don't.
The booting time takes maybe a minute or two longer, if booting from an external drive. But far more useful and safer, more mobile. In your case, the added advantage is you can do this with ANY distro, see which ones you like.
Edited by brainout, 20 September 2015 - 02:09 PM.