The elephant in the room these days is Adobe - products you can only rent them by the month now, you can't buy a disk and keep using it till you decide it's time for an update. I use all of the Microsoft Office software (Word, Excel, occasionally PowerPoint, and I have plans for the database Access) - I just tried opening the Apache OpenOffice software and it can't see any of the .docx files, though I haven't updated it in ages. And when conducting a search about upgrades, I found this: Why you should ditch OpenOffice and use the free LibreOffice suite. (The Apache software shows up as installed in the computer but the Apps list doesn't give me a clue as to where it might be or what it's called to uninstall.)

I do use the Pro version of whatever Windows OS I'm using, and that's either installed on some of the computers or purchased as a retail upgrade disk or thumbdrive. I prefer to have a set up backup disks for the OS, but that is scarce these days. I want a clean install so I don't have to deal with Win7 backup software in Win10 and such - the old software doesn't always play perfectly with the new. And it messes up the firewall.

I run two computers into one monitor using different input ports - VGA and DVI. One button-press to switch over.

You use a KVM switch for this - keyboard and mouse through it also? I read the linked article and took a look - I have several ports into the monitors I use, so that is doable. Mine are connected using HDMI cables. I also wonder about setting up the old computer without any monitors attached and using remote desktop - does it need to have monitors up and running to use it remotely? I have one old monitor I could hook up to it, but to use the software in that machine remotely - you see that I can't use the same two monitors simultaneously unless the presence of the switch lets the old computer think it's displaying. It's easy to overthink this, and resolve to just buy the new software and be done with it. I have several little-used programs in there that I'd also want to update and install. The list is getting longer (I use Nuance's OmniPage for OCR work, and I have a lot of articles to scan and OCR from my grandfather's writing). I have stuff from my father to process (having a second computer working on some of this stuff would save me time) but the Nero software in the old computer can't also be loaded in the new computer. . .