What a relief! All the files from my crashed hard drive were recovered and I have gotten them back on an external hard drive and backed them up twice. I still have to get my primary computer fixed, but now at least I can get back to the work of writing without having to worry about the lost chapters.
I am grateful to the people who recovered my data. They are heroes. But no explanation was ever given as to what might have happened to my hard drive. In the end I can only conclude that it was the victim of some evil magic.
I narrowly escaped disaster, but at a great monetary cost. If you have important files that you would pay to get back, or that would just be a major inconvenience to lose, save yourself the trouble and money and make regular backups. With computers the chances are good that sooner or later some evil magic will strike and trust me, you’ll be a lot happier (and wealthier) if you have a current backup.