Don't know why you are downvoted. Before I switched to Mac (now I know what a good choice I made!), I find that installing fresh Windows without piracy is incredibly hard. The so called OEM embedded serial key works only sometime; Other times, the fresh Windows will ask me to buy and activate it. Utterly confusing even for a techie like me.
Dealing with the windows tax crap is hardly news, buying new overpriced hardware to benefit from a golden prison is neither an acceptable solution for somewhat facing the issue nor what a techie would do.
The easy option is to phone microsoft support and explain the problem, you most probably will be given a new valid key. Other options for techies includes using OEM install medium or installing a free software OS.
Nowadays there's no licence key to type anymore, it's included in the hardware sold with windows 8 (which is worse).
So I installed a pirated Windows.