Windows 7 having trouble, is it counterfeit, i really not think so, wife bought it at Currys?

I have had windows 7 for just over a year, my mrs got it for me for Christmas, but i sometimes get this thing from , Apparently windows7 saying i have got a copy, and it is counterfeit, and i should go to this site and purchase the genuine article. Is this a scam, or what.. It seems very genuine, but i dont know, appreciate any answers or solutions. cheers Terry