So, my dad recently bought an HP laptop from a guy at work. It didn't come with any discs or anything. Everything was running fine for a few days until yesterday the desktop background went black and at the bottom right corner of the screen it says "This copy of Windows is not genuine". It has also started prompting him to activate windows upon load-up but the windows activate key on the back of the laptop doesn't work. Could the guy he bought it from have installed a non-genuine version of windows? I have an old Windows 7 installation disc which I tried using to reinstall it but it wouldn't let me. Any help would be appreciated, thanks!
Edit: The other thing is that there is a Windows Vista sticker on it but it appears Windows 7 is installed. Also, when I try to look for Windows updates it says none have ever been installed and it just searches for updates endlessly but never finds anything.