Microsoft's Windows 8 operating system will be available from retailers on October 26th, but up until now we haven't known exactly how. Amazon has several listings today for Windows 8 upgrades, including a European N edition that is marked as "not with Windows Media Player." We exclusively revealed the box art for Windows 8 earlier this year, and Amazon's imagery matches it.

One listing for a Windows 8 Standard Edition to Windows 8 Pro Edition shows that Microsoft will be offering product keys in retail packaging at launch, with no disc required to upgrade to the Pro edition for Windows 8 users. The online retailer hasn't listed any pricing against the Windows 8 listings, but Microsoft has previously said that existing Windows XP, Windows Vista, or Windows 7 users can upgrade to Windows 8 Pro for $39.99 online or $69.99 in stores.