I have backed up my files to disc, memory sticks and hard drives.
In 2010 I registered a rough draft of my novel and future ideas, in the UK with
http://www.copyrightservice.co.uk/
In 2013 I registered my novel and future ideas, in the USA with
http://www.copyright.gov/
That's an interesting question, Adrian. I do back up my work but hadn't thought of registering the copyright. I have multiple printed versions with notes etc for changes and updates, so always thought I could rely on those. I'm careful who I give it to for reading purposes, and usually give out a hard copy rather than digital version.
I will look into the copyright service as well, I think. I wonder if, once you get an agent, they will manage this side of things?