I am getting ready to burn an ISO of the Ubuntu OS to a USB drive. Where do I find and download the ISO file? Do I need to download the entire OS, and if yes, does this impact my current Windows OS? My goal is not to replace my current Windows OS but to use the bootable USB to get into a computer I inherited that has Win 8 and is password protected. I was told that I could bypass the password if I booted with a Linux OS. This is my last resort before simply ditching the computer.
You're not looking for Ubuntu. There is a Linux distro which is designed to kick the password query out of the ram of Windows. However, since as a Windows user you don't know how to make a bootable device, it'd be easier just to use the protected mode / save mode (whatever it's called on Windows, everyone I know uses Windows in German, therefore I only know the German word for it) to replace the password with whatever you want to replace it with. If you boot in the protected mode / save mode, you can log into the admin account without password. Since you're new to this page: Please press the tick on the left it this solves your problem.
You can find all the information that you need @ http://www.ubuntu.com/download/desktop/create-a-usb-stick-on-windows. These steps will not hurt your current windows system. You can download the iso file from http://www.ubuntu.com/download/desktop