This might not seem a major issue, but if you decide to change the motherboard on your PC, then chances are you'll also need to pay out for a new copy of Windows at the same time, as the old one won't re-activate on the new hardware.
To see how you can reuse your retail Windows licence read our How to install Windows on more than one PC feature.
Should I buy a cheap OEM key?
There's nothing illegal about buying an OEM key, so long as it's an official one. There are plenty of legitimate sites online that deal in this kind of software, Amazon has a number of sellers offering OEM keys, as does eBay, and more specialist sites like the aforementioned Kinguin.
Just be sure to read the description carefully and check user ratings before spending any money.
So long as you're happy to take on the responsibility of being your own technical support, then an OEM version can save a lot of money while offering an identical experience.
Of course, those who prefer peace of mind, and someone at the end of the telephone who can help fix any problems, might prefer the full retail route instead. Just avoid buying a DVD version from that dodgy-looking guy in the Tesco car park.
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