Upgrading my daughter's motherboard

Honestly, I'm not sure what version she has, all I do is pay the subscription every month. I'm the PC build nerd, she's the photoshop junkie. ( HG-The-Hamster (Kayla) | DeviantArt  ) I imagine she keeps everything up to date so I'm guessing her version is CC whatever.. 2019??

I've done PC builds before where I removed the SSD/M.2 and placed it on another board, and of course, you have to re-activate Windows, no biggy there, been there done that too many times to count. I just wasn't sure how photoshop handled registering and account info. But yes, been through it when I bought her a newer laptop to replace her old one. I deactivated it in the adobe control panel on this site, then reactivated on her new machine. The reason I am a bit confused is because when I did THAT setup, she went from having all her old data just transferred onto a clean, fresh setup via USB stick. On this one coming up, I wasn't sure if this was handled in the registry or how that worked exactly, so figured I'd better ask. I might later on do a fresh install of Windows 10 on it for her, but ATM I'm kind of on overtime at work and don't really have the time to commit to transferring and backing up all data, and, since she's older now, I make her buy her own upgrade parts so she'll have to invest in a new SSD/M.2 later on.

ericc38134630   I can't see anything about what Photoshop version you are talking about?  If you have a Creative Cloud subscription, then you don't need to deactivate.  In fact there is no provision to do so.  You just sign out and in to the Application Manager

But you don't need to do this.  You appear to know that you can have two installations of Photoshop active at the same time (but only use one of them).  I have my CC apps installed on three systems (desktop, laptop and a Cintiq Companion 2).  I never sign out.  I just sign in to either of the two portable devices as and when, and it automatically signs me out of the other.

But if you are talking about CS6 or earlier, then absolutely, don't even think about not doing it, deactivate before you start messing with it.

But the bottom line here, is that what Dag is telling you is true.  Your Windows operating system, and apps like MS Office will use the system hardware to identify the system, and there is every chance that the new motherboard will break that link.  Is the OS an OEM version?  i.e. did it come pre-installed on the system when new?  If that is the case, then you might find not even Windows will work, yet alone Photoshop.

https://www.techadvisor.co.uk/feature/windows/cheap-windows-keys-3665849/

It doesn't end there.  I would not even consider changing the hardware to that extent without a clean install.  Not only will it give you a _way_ less problematic user experience, it will probably be quicker in the long run.  Otherwise you'll be chasing annoying difficult to solve problems for ages, and you'll be unlikely to every get it completely OK.

Make a plan.

Fit another drive, and move as much as you can to the new drive

How to Change the Location of User Folders in Windows 10 - dummies

Install WinDirStat so you can chase down everything that's left on the C: drive, and copy to the new drive.

I'm in the process of reinstalling Windows 10 because Logitech G-Hub stuffed it up, and I've made things worse trying to fix it.

This is what my C: drive looks like in WinDirStat.  Clicking on a folder shows you the graphic representation of the drive space it uses, and more importantly, clicking on a data chunk shows you the folder.  It's a godsend for a disaster proof OS reinstall.  The green rectangles at the bottom represents the Recycle bin, the muddy pink bottom right is pagefile.sys, and one file you don't want to mess about with (leave it where it is). 

WinDirStat is completely free

https://windirstat.net/

What app version is it?

This isn't merely a new motherboard, it's a new machine. It is guaranteed to trigger activation failure in every piece of software that uses it, including the operating system. This is precisely what an activation system is supposed to flag.

I wouldn't even think about it unless I was prepared to rebuild everything from a fresh OS install up.