Well, on my PC I've been using for a while, it's been all fine until recently (I went into system repair mode, nothing was wrong) so when my pc rebooted itself on the bottom right there keeps popping up an icon saying my Windows isn't genuine? (also makes my background completely black). What do I do? I was thinking about using the MBR regenerator and stuff but reading it makes me think it removes all of my stuff? I don't want to completely wipe my computer clean (has 300+gb of stuff). Please and thanks if anyone can help! Oh and I'm using Windows 7 Ultimate (x64)
That tells me you're trusting your drive to never fail and you have no backups. You need to do what acrsn says, but if your 300+GB of data is not backed up you need to fix that too.