I think all of this might have been a blessing in disguise. I bought a new external hard drive and have just spent a day sorting and backing up my 'Windows.old' - which stored all the files from my old installation when it reinstalled Windows - directory onto it, and deciding what to keep overall and/or in my new installation. Basically Kon Marie-ing the whole thing, and now it's done and just feels so streamlined, as if I've got a whole new PC... there was just so much clutter and it's all gone now, and feels really good. Now it's just about looking into better backup solutions for going forward, such as Acronis as suggested, but actually pretty happy right now, and very happy with my new drive as well, so all's good 
