Message Telling Microsoft Not Genuine / Valid

Last week I had to use my laptop. When I got to windows it had a message telling me that windows was not Genuine. I did a check and Microsoft said it was not valid. Given the fact that at the time I did not know it was hacked or could have been, I just closed it and began back on my desktop which is my main computer. This also is a wireless network. Tonight I did a reboot and the same thing happened with my desktop. I again went to microsoft and again the told me the key was invalid for this part of the country whatever that means. This desktop was bought at a computer show a couple years ago and has been dam good to me. It is a Dell. I don't know what to do. Someone told me about a keyfinder but I don't want to do anything until someome advises me....