ok sooooo I need help. Here's the situation:

My desktop has gone black and on the corner it says this " Windows 7 build 7601 This copy of Windows is not genuine" and I'm constantly getting pop ups now saying "You might be a victim of fraud" "Get genuine Windows 7"

I asked the actual owner of the laptop  Demonicbolt and he said to get a Hacker code. Well I got one and now I don't know what to do with it. I'm 100% clueless right now. Can someone please tell me what to do. In the simplest way it would be greatly appreciated