Some of us never do it but we all mean to - back up our files.
For some unknown reason a few weeks ago I bought an external hard drive - maybe because my hard drive was filling up with images.
Last Monday my system crashed for no reason at all and I had to re install windows,a long terrifying job for a guy who is not over computer savvy.
Reloading programmes was a total time consuming pain as well as realising all the other junk we accumulate that we rarely use but need,like QuickTime player and acrobat etc.
Then of course if you haven't noted things like  e mail addresses and passwords etc then you face another dilemma
I had already put all my images onto the external drive but if I had not I would of lost several years of work,and not just the images but the travelling and walking involved in getting them.
So guys and gals be warned - it can happen - if you haven't backed up your images and important files DO IT.