Buy a new license and reinstall...?
That is going to be my course of action. I will first call MS as Yodap suggested and maybe they have other suggestions.
I will most probably go with the OEM version. By the way, what does OEM stands for?
The least expensive Home Premium key for sale I've seen at eBay is $50, which isn't bad, but one can get the boxed OEM version with disc (32 bit or 64 bit, not both), for about $99.99 at Newegg.
Please see this stress reducing video.Any ideas what to do? If I ever bump into that SOB who sold it to me, I am going to break his knee caps.