Windows XP PRO doesn't accept original OEM key

I assume you can install with the key that came with your version of xp pro.
The original OEM keys are tied to the disk they came with, so you won't be able to make it work with those specific keys.
Or you need to install your version with the dvls key.

What you need is to remove this key after you install xp and generate a new one for yourself. Hopefully this is what you want to do.

That gets you a clean licensed key.

Dr Pete