thank you internets

New hard drive it is. While my poor sick toddler naps, I shall find the various recovery/install discs that came with the desktop, let the current drive imaging run and if it completes successfully create a rescue disk, if not do as much pulling-of-data as I can, and then go get a new hard drive installed. And it appears that Macrium will let me restore to a drive of a different size, so I will take this opportunity to upgrade the size too.