This copy of Windows 7 is not genuine Build 7601

Hi, My PC is almost 4 years old. It was bought from EBuyer in the UK and had Windows 7 preinstalled with the C OA sticker on the side of the PCU box. Yet for some reason it has now suddenly started to give me the above message in the bottom right corner of the desktop. As yet the screen has not gone black as seems to happen with some other instances of similar problems. However Windows...