I agree. You should contact them to get this resolved, because you'll soon be blocked from getting important updates. It may just be a matter of verifying the # again to get this fixed.
Microsoft is in the process of identifying and cracking down on versions that were installed more than once, and for now theyre just popping up that window and they'll also prevent you from doing a WINDOWS UPDATE if you try. (automated ones still work for now, but that is changing in a few months)
They will be doing the same thing very soon for the Microsoft Office product.
When you buy these products, the fine print says that you're only buying the license to use it and don't own the product. It's only valid for the original pc, and non transferrable if you buy a new PC. The security checker will often reject you if you upgrade some components in the PC, because it looks at things like the hard drive's serial #, the cpu serial # and speed, etc. (to make sure its not being transferred to another pc)