My main desktop dual boots Windows 7 Ultimate and Windows 8.1 Pro. I use 8.1 predominantly, but also keep the Windows 7 side up to date, and there are a couple of programs on that side that don’t run on 8.1. The 8.1 side will be an easy enough upgrade to Windows 10, which I’ll do to take advantage of the free upgrade, but then I’ll make a drive image of 10, and restore my 8.1 drive image for continued use.
The 7 Ultimate side, however, won’t directly upgrade. It’s carved up and spread over two separate HDD’s (Hybrid Disk Drive), so I’ll have to either put it back together (which can be done) and then upgrade, or upgrade just the 7 Ultimate partition, which will not save apps and settings, and then start re-installing stuff. Either way is a bit of work (there’s a lot of stuff). I have up-to-date drive images of the different partitions that contain 7 Ultimate, so I’m protected either way.
The third option is to do it both ways, making drive images along the way, then decide which option works best for me. But it’s obvious with the new OS model MS is introducing with Windows 10, an OS upgrade could be released at any time, and a split-up system like I’m running now with 7 Ultimate simply won’t allow for an upgrade installation that keeps everything intact.
It’s gonna prove interesting, regardless.