>I'd generally recommend against "in-place" upgrade. My upgrading from Windows 7 to Windows 10 went reasonably smoothly (actually it went a lot better than I thought it would), though not without a few worrisome "hiccups", and still required reinstallation of a few applications to correct some "quirky" behavior.

That being said, nine days ago I installed the OS three times. The kick was to write the boot into the 2nd disk, but it kept writing it in the first... which I eventually accepted and allowed it to boot from there. And guess what, in the boot menu it also offers to boot from the 2nd disk... so OK, I went with that and it still works (and I've rebooted ten times since, for various reasons).

The nice thing is that each app found its old settings, up to the MRU lists or game scores. Even the apps I almost forgot and had actually uninstalled years ago, tried again and they still stuck to their then setup.

The only trouble came from my trying to reshuffle disks in a way I thought would be easier... well it isn't. Put them back the default way and now everything is as it was, except I like the current flavor of the OS better than I liked the previous one.