Under sound advice I've backed-up my work on 4 seperate hard drives, as well as the files I have saved on Google Documents. I can't express enough how useful Google Documents is for writing from pretty much anywhere, so long as there's an internet connection available.
I've compiled the seperate chapters into a single "first draft" file, which I've converted to pdf so it can be proof-read. I know full well that things need to be changed, not just in terms of possible spelling or continuity errors, but also because of differences in personal taste. If I'm to get published, my work has to appeal to the widest possible audience, and I know my ego has to take a back-seat for this to happen.
I'm oddly calm and confident about this. I actually want to hear criticism so I can learn and grow as a writer. I know that, several years ago, I couldn't have honestly said that.