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Windows 8 is providing an upgrade option to add features to your PC to get a different Edition of Windows 8. Earlier in our article, we had seen how Microsoft has simplified the various Editions to be made available for Windows 8. So let us see how its done!
Add Features To Windows 8
From the Control Panel, go to System. There you'll see the link “Get more features with a new edition of Windows”. 
Another way is from Start screen. Place your mouse at top right to get Charms > Search for 'Add Features' and click on Settings. There you see 'Add Features to Windows 8'. 
When you click on it you get: 
We can see that you can buy an upgrade online with a previously purchased Product key or can buy a Product key online to upgrade. In Windows 8 Release Preview, click on 'I already have a Product Key'. The 'I want to buy a product key online' option will be in place in future final editions. At most you might see some dummy representative offerings if you want to just try 'I want to buy a product key online'. So when you click on 'I already have a product key', enter this Product Key Specially provided for upgrade of Release Preview Edition. For the RTM final version, you will have to buy a license.
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Click Next. Please note that you'll have to Enter this key only (or purchased for upgrade in future) and not the one you entered for Windows 8 Release Preview. 
Now, to get this screen, check 'I accept the license terms' and 'Add features' button. 
This will start the process of Adding Features. It may take a while depending on your PC - if it needs any updates. Your PC will restart at least once. For me it took just 2-3 min and it restarted twice. 
Now once all is done, you will find that your Windows 8 PC is ready with the upgrade. 
Add Windows Media Center to Windows 8 RP
Actually in this Windows 8 Release Preview, this Add Features, adds the Media Center and thus that's the upgrade version. The license key provided was also for adding Media Center only - as stated in the official FAQ.
Windows Media Center is not preinstalled in Windows 8 Release Preview. If you want to use Windows Media Center, you need to add it.
Thus after the upgrade, we can see the change of Windows 8 Edition as mentioned in Control Panel > System. 
It now says - “Windows 8 Release Preview with Media Center' while as seen in our first screenshot it was 'Windows 8 Release Preview'.
For the Windows 8 RTM final version, you will have to buy a license.
In Add features to Windows 8, you can get an edition of Windows 8 that has more features than your current edition. To get a new edition, you need to buy a product key-they're available at electronics stores. Make sure to buy a product key that's specifically for Add features to Windows 8. And you can also buy a product key online in some countries and regions. Once you buy a product key and enter it into Add features to Windows 8, new features will be added to your PC automatically and you'll have a new edition of Windows 8.
So this is how you'll be doing real world upgrades when you want to Add features by getting a different Edition of Windows 8.
Go here if you cannot add features to Windows 8.
