Why is my microsoft office suddenly not genuine?

I've been using my Microsoft office for quite a few years but all of the sudden I get a message saying its not genuine and when i run the validation thing, it says the code belongs to a large corporation or something. WHY???? I have 4 days left before it is marked as not genuine. What happens when its marked not genuine? Why is this happening? How do I fix it? PLEASE HELP!!!!!! thanks in advance