If you already have a standard version of Windows 8.1 and want to upgrade to "Pro" or add specific capabilities, you can use the tool:
: Sites like Mr Key Shop and ESDcodes offer digital keys with instant email delivery. buy windows 8.1 64 bit
: eBay and Amazon often have listings for physical "Retail" or "OEM" boxed versions. If you already have a standard version of Windows 8