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).