I am a genius. Well not exactly.
Since I was sick I didn't have time to rearm windows due to which it expired. So I booted it "with limited functionality". In the opened up Firefox window, I put file > open. Then, in the dialog box, I searched for cmd and ran it. The command window opened up, I entered the slmgr thing, and restarted. Saved me the trouble of going through the installation again....
Didn't know where else to say this.