Upgrading to X99 New OS?

I am upgrading my system to X99 over Christmas which means that I will be getting a new CPU and motherboard. Will I have to get a new windows key or will my old key work? If I have to get a new windows key what is the best way to get a legitimate key cheaper? Would a windows 7 or 8 key work or would I need 10 because that is what I currently have? Thanks for the help!

If you have a retail key, you can transfer it over. You may need to call the automated phone activation line.

If you have an OEM key, technically you can transfer it over but it's a violation of Microsoft's EULA and hence piracy, so to avoid getting in trouble myself I must now look disapprovingly and urge you not to do it.

If it's an Intel>Intel upgrade you should not need to do anything with the OS. It should just work. If it's AMD>Intel, you're going to need to reinstall everything.

@OldDaddyG Microsoft do not generally consider performing a mobo and CPU upgrade as counting as an entire new system. If you only have an OEM licence you will likely need to reactivate Windows manually, if you have a full retail license you probably won't.

In the Vista era, it wasn't uncommon for a Hard disk and RAM upgrade to trigger reactivation, under Windows 7 the weighting was re-balanced and more components would need to change. Mobo and CPU are weighted heaviest and RAM lightest. Hard disk and GPU are somewhere in between. I am not sure how it is weighted in Win 10 but it's probably the same as Win 7.