Analysis of information sources in references of the Wikipedia article "Windows 8 editions" in English language version.
To enable sideloading on a Windows 8 Enterprise computer that is not domain-joined or on any Windows® 8 Pro computer, you must use a sideloading product activation key. To enable sideloading on a Windows® RT device, you must use a sideloading product activation key. For more information about sideloading product activation keys, see Microsoft Volume Licensing.
...be sure that SUA [Subsystem for Unix-based Applications] is installed on the target computer. On computers that are running Windows 8 Enterprise, open Control Panel/Programs/Programs and Features/Turn Windows features on or off, and then select Subsystem for UNIX-based Applications.
Can I add features to my Single Language edition of Windows? Yes. If you bought the Windows 8.1 Pro Pack or Windows 8 Pro Pack, you should be able to install it and activate Windows successfully.
Can I add features to my Single Language edition of Windows? Yes. If you bought the Windows 8.1 Pro Pack or Windows 8 Pro Pack, you should be able to install it and activate Windows successfully.
And if you want, you can add Windows Media Center for free through the "add features" option within Windows 8 Pro after your upgrade.
You can add Windows Media Center for free through the "add features" option within Windows 8 Pro after your upgrade.