old windows 10 on new pc

[amnesiabro23]

so i just built a new pc and used my old hard drive and it still has windows 10 but the problem is that there is a watermark on the bottom right of my screen that says activate windows and when i do that it says we can't activate windows on this device because you don't havee a valid digital license or product key. should i have to buy windows 10 or a product key? also a little info i upgraded for free from windows 8.1 back when windows 10 first launched.

 

[Dugimodo]

Your licence is tied to the old motherboard. If you have a retail copy of windows it can be transferred and if it's OEM it is supposed to stay with the hardware.
If you use a windows live login and the key is tied to your account you may be able to run the activation troubleshooter and transfer it over.

Otherwise you may have to ring MS and explain the situation and see what happens. There's a number somewhere in the options when you try to activate.

 

[USAFRet]

so i just built a new pc and used my old hard drive and it still has windows 10 but the problem is that there is a watermark on the bottom right of my screen that says activate windows and when i do that it says we can't activate windows on this device because you don't havee a valid digital license or product key. should i have to buy windows 10 or a product key? also a little info i upgraded for free from windows 8.1 back when windows 10 first launched.

If you had done this before changing parts, you could have activated it in your new hardware:
https://support.microsoft.com/en-us/help/20530/windows-10-reactivating-after-hardware-change
http://www.tomshardware.com/forum/id-3164428/windows-build-1607-activation.html


Now, your only recourse is to call MS and plead your case, or buy a valid OS for this new system.

 

[amnesiabro23]

So pretty much i have to buy windows 10 so what should i do buy retail or oem

 

[USAFRet]

So pretty much i have to buy windows 10 so what should i do buy retail or oem

It does not really matter. The line is significantly blurred.
Previously, OEM was tied to the first motherboard you installed it with. Not anymore.
See my links above.