I did this a long time ago, but recently installed Illustrator CS3 which broke everything, not because the software won't work on Windows 10, Photoshop and CS3 do work on Windows 10, but because when you install it, and enter the licence, you then need to activate it.
Skip my rant about how much I hate Adobe and why unless it helps because you're already starting to understand how much and why...
Needing to activate would be fine, except Adobe have decided in their greed frenzied capitalist wisdom not to offer the ability to activate it anymore. You just can't, they won't let you. You may have paid a thousand pounds for the software, but they've decided it's not going to work anymore.
Well, we can get around that...
I had a perfectly working version of Adobe CS3 running, just using Photoshop and Dreamweaver... but realised I needed Illustrator for some vector shenanigans. So I installed Illustrator from my perfectly paid for and legitamate disc, only to have Adobe in their wisdom stop everything from working.... until I reactivated it, which would be annoying enough if they still had an activation service running; They don't. You can't. They just break your software for fun. Well, more likely for money, because that means you have to rent their new version.
My guess is they realised they peaked about ten years ago, Photoshop already did what most people needed it to do, and now they figure the only way to make money is rent the software, rather than selling it. CS3 to them is what stops them renting to everyone. They're like a dodgy estate agent, who sold you a house, who then burns it down so you still have to rent their new ones.
So if you've got a legit bought and paid for version on an old computer... or you just want to update your operating system, and still keep Adoby CS3 (or possibly CS4 or CS5) running, how do you do it?
It's actually quite simply once you know, but it took a lot of digging to work this out. I'm partially writing this to remind myself how if I ever need to do it again, partially to vent because... just because... seriously, how can you charge people thousands for software and then intentionally break it.... and of course if it helps anyone else avoid having to pay rent to Adobe for software they've already paid for, that is a massive bonus.
Many people think the licence information for Adobe CS3 and Photoshop is held in a windows registry key; It is not. It is held in some files in the folder :
Windows (C:)\Program Files\Common Files\Adobe\Adobe PCD
or depending on your operating system it might be
Windows (C:)\Program Files (x86)\Common Files\Adobe\Adobe PCD
There will probably be two folders and a file in there:
cache
cache backup
and pcd.db
Just copy those files from the old computer, to whereever Adobe have put them on the new one - under Program Files, or Program Files (x86), and you should be good to go.
A couple of notes: You might well need admin privelidges to do so. I found it helped to delete the files first that I was over-writing as the OS refused to over-write them first time. The usual common sense rules apply - back up anything like this before over-writing/replacing it, just in case.
This is the bit that's going to be painful.... if you don't have old copies of those files because you've already updated your OS or wiped them... you might be out of luck. If you've only just over-written those files, you might be able to roll back your system to get the old ones back... maybe...
Other than that I hope it helps, and if this works for you, I do take tips; You can buy me a pint (or a half) here. Hopefully I saved you the headache this caused me regardless of whether you're feeling flush or not.