Hi i need some advice. I brought a computer last year with Windows Home pre installed on it. Since then I have upgraded my graphics card from a 5200 to 6800. My DVD rewriter broke so i ordered a new one from overclockers, after i put it in, Windows is now saying my hardware has changed significantly and i need a new key. Does this mean i now have to buy windows again? I have tried entering my key again but it just says it is invalid 