I have a Dell Inspiron 2330 all in one out of warranty. Originally came with Windows 8 and have since updated to Windows 10. Well it would not post and had to replace motherboard and reinstall Windows 10. Of course Windows will not activate since it is a new motherboard. The PC also did not come with an OEM sticker for Windows and the key is unrecoverable as the old motherboard would not post. I called up and said there was nothing Dell could do and a new purchase (over 100 dollars) of Windows 10 was needed. Am I not even given the choice to go back to Windows 8 with license key for 8? This is unfair. Your motherboard went bad and believe I should be given at the very least a license key for Windows 8, the possibly by supplying that to Microsoft they would honor my upgrade back to Windows 10. Bad business Dell if this is true!
No need to pay anything. Microsoft has instructions here--
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.
If it is an OEM version there is nothing you can do. I had the same issue and was able to retrieve my License Key, but since the MB was changed it would not accept it. Just another way dell screws you. I spent hours with tech support arguing and all that they would say is if you did not buy the MB from Dell you do not have the software license any more.I had to purchase another license key. I will never buy another Dell again!