Before purchasing a new key, it is worth verifying if you already have one available to you: Find your Windows product key - Microsoft Support
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: Provides Windows 8.1 Professional OEM keys starting at roughly $21.18 . Before purchasing a new key, it is worth
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: A more traditional vendor that often carries full retail versions or digital license keys, ranging from $82.49 to over $200 for original retail boxes.
: Offers digital keys for Windows 8.1 Professional (OEM) at competitive prices, typically around $16.38 .