Sorry to say I upgraded to 8. Same for my other computers, flawlessly. Do I need to purchase an installation disk or can one make their own disk from the download of win 8 file (which I probably don't have anymore because of various troubleshooting steps). I had the firewall deactivated. The problem started as soon as I upgraded. Seems as though you have hit the solution ... a clean install.
I would say you got lucky with the ones that upgraded 'flawlessly' and I know however well they are preforming now, they would be performing even better from a 'clean' install.
No you should not need to purchase an install disc. I believe (I could be wrong) the install file is an .ISO and you could burn it to a disc (using one of the existing Win8 installations since they easily handle burning of ISO files built right into the OS) and then use that disc on your hubby's machine.
Like I already said, I ONLY do clean OS installs. I have never done an 'upgrade' install (at least not on my own machines) and never will. Clean OS install means clean driver files, clean registry (in my opinion 'registry cleaners' often do more harm than good since some of the 'orphaned entries' they claim can be removed can actually still be important etc.), clean drives/partitions, smaller winSxS folder (if you're upgrading from Windows Vista or newer), non-corrupt system files and/or program files, etc. etc.
Yup.......clean install is definitely the way to go!