I am holding onto the disc, purely for the reason you stated!

What I want to know tho, is if Windows fucks up, is there anyway I can boot up with Ubuntu from CD, and then access files/data on my C: (Windows) drive to safely squirrel it away before reinstalling Windows on the C: drive?

also, by having this CD, does that mean I can boot up a computer that doesn't even have a HDD in it? So say I had a system complete except for a HDD, boot up using the Ubuntu CD, and access files (music, video etc) from a USB HDD?