Does anyone know why this is happening to my computer?

All of sudden my computer is saying, (your system may be at risk) I click on it and a page comes up and this is what it says, Windows XP Genuine Validation Results. below reads, This copy of Windows did not p Genuine Validation( the product key found on this computer is a volume license key (VLK) that has been blocked.What the heck happened and how do I fix it?