Sanderxpander
Huh, I guess I've never tried phone authorization, I understood OEM meant "tied to the system" which I assumed to imply mobo. I wonder if they have a number over here or if I'd need to use the US one. Thanks, I learned something!

As long as it's the same machine being repaired/upgraded (not being moved to a second physical machine), you're fine.
 
If Windows gives a BSOD with the new hardware, the OP can use something like Acronis Universal Restore.
 

Sanderxpander
Huh, I guess I've never tried phone authorization, I understood OEM meant "tied to the system" which I assumed to imply mobo. I wonder if they have a number over here or if I'd need to use the US one. Thanks, I learned something!

The OEM licenses I used were obtained without hardware, intended for system builders.  Can usually be found online at places like Newegg or Amazon.
 
Never tried it with an off the shelf OEM PC license.  But that would be difficult to upgrade mobos in anyway, compared to a custom built system, due to the typical proprietary case form factors used by OEMs.
 
When the online activation fails, you can use the manual offline method. 
 
To activate Windows 7 using the phone:

Select the Start button, right-click Computer, select Properties, and then select Activate Windows now.

Choose Show me other ways to activate.

Type your Windows 7 product key, and then select Next.

Select Use the automated phone system. You may be asked for an admin password or to confirm your choice.

Select your location (or the location nearest you) from the drop-down list, and then select Next.

Call one of the available phone numbers listed. An automated system will guide you through the activation process. 
https://support.microsoft...ting-microsoft-windows

Jim Roseberry
 
If Windows gives a BSOD with the new hardware, the OP can use something like Acronis Universal Restore.
 

The OP is working with XP.  Would that still be a good option for an unsupported Windows OS?

I believe Acronis Universal Restore is compatible with WinXP.
It's been a while since I've used XP... so someone correct me if I'm wrong.  
 
The OP can also manually uninstall components... and shut the machine down.
When migrating the OS to the new hardware, Windows will then load necessary drivers.

I've never had any luck upgrading hardware without a clean install of Windows. I've been building PCs since Win 95/98.
 
Last time, I even tried using the Microsoft sysprep method of moving Windows 7 Pro to a new motherboard.
https://technet.microsoft...cc721940(v=ws.10).aspx
 

What is Sysprep?

The System Preparation (Sysprep) tool prepares an installation of Windows for duplication, auditing, and customer delivery. Duplication, also called imaging, enables you to capture a customized Windows image that you can reuse throughout an organization.

 
It failed, apparently because the Win 7 version I had installed was pre-SP1, with SP-1 applied after original install.  That turned out to be unsupported for sysprep.  A couple of days wasted and I still had to clean install.
 
That brings up probably the greatest new feature in Windows 10.  It has a new Windows hardware abstraction layer that allows hardware changes without even blinking.  I have heard several recent success stories of motherboard swaps that went without a hitch! 

I had Win 10 Pro (with "Digital Entitlement") on my old DAW system.  I built a new system and moved the OS drive (a Samsung 850 EVO 500GB) from the old PC to the new one.  Booted up and Win 10 did what it needed to do including installing the new hardware drivers and I was up running on the new system, activated with the Digital Entitlement, in short order.  
 
I did have to reauthorize a couple of plug-ins but nothing else.

abacab
I've never had any luck upgrading hardware without a clean install of Windows. I've been building PCs since Win 95/98.

I prefer a clean install.
There are cases where I'll migrate.
ie: My main studio DAW undergoes hardware changes on a regular basis.  
I generally keep the OS clean/lean... and have little trouble migrating Win10.  
 

Jim Roseberry

abacab
I've never had any luck upgrading hardware without a clean install of Windows. I've been building PCs since Win 95/98.

I prefer a clean install.
There are cases where I'll migrate.
ie: My main studio DAW undergoes hardware changes on a regular basis.  
I generally keep the OS clean/lean... and have little trouble migrating Win10.  
 

Agreed.  A hardware migration is supposed to be completely transparent with Win 10 now.  I'll probably get to test that out on my next hardware upgrade! 

This last migration, the Microsoft agent wanted a receipt for the copy of Windows.  
I'm like... uhhh... I've got the copy right in front of me (jewel-case and all).
Had to take a picture of the Install Code... and leave that on the desktop for the agent to authenticate. 
Minor annoyance... but all was fine.  
 

I guess that there might be a few variations to the process, based on whether you already had a digital license for Windows 10, or whether you have a product key from a retail package.
 
https://support.microsoft.com/en-us/help/12440/windows-10-activation
 
Activating Windows 10 after a hardware configuration change
If you made a significant hardware change to your device (such as replacing the motherboard), Windows 10 might no longer be activated and you might see the activation error codes 0x803f7001 or 0xC004C008. If you're running Windows 10, version 1607 or later, and added your Microsoft account and linked it to the digital license on your device, you can use the Activation troubleshooter to reactivate Windows. For more info, see Using the Activation troubleshooter.
If your Original Hardware Manufacturer (OEM) changed the motherboard for you, your PC should reactivate automatically or you should be provided with a replacement product key. If you see the Activation error “Unable to reach Windows activation servers” then follow the steps in this additional help article.