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/
Having spent many years in I.T, I have seen Malcolm's experience many times. Hard drives do die, and the recovery options span very expensive to impossible. Backing up to removable drives is fine, as long as you test the recover-ability once in a while. I have seen countless instances where backups from various media forms were unreadable. Another consideration is burglary, fire, flood, whatever... Always have an off-site copy of all critical files.
Today, almost everybody has access to some form of online storage, and this, in my opinion, is the most secure way.
Andrew Lockhart: "surely the best thing is not to put it out there until it is finished and published in print or digital form" -- sounds good to me.
Thank you for the extra info, Adrian.
I continue to back up to memory sticks (more than one) but rarely print out hard copy.
Helen, I'm sure that has happened many times.