Compaq Presario CQ56 Invalid Serial Help...?

Ok, turned on my laptop this morning and everythings fine, leave it to go for a cigarette and come back to find my background has gone black and apparently my copy of Windows isnt genuine, so turn it off and on and am greeted by a message on the startup screen that my product name, serial and various other things are invalid or missing.

Wrang HP who basically said i can either pay £15.99 to speak to a Tech who has no guarantee of fixing it or i can take it in for repair. Surely theres a simple fix to this?? I suspect a virus thats just trolling me since when i attempt to verify my copy of windows it makes me download something then tells me my copy is couterfeit (its not) and that i need to pay £70 for a new one.

Any help or tips on this would be greatly appreciated, im going to run Norton and MalwareBytes and see what they drag up.

ThanksXx