We know that Windows 8.1 would be an update for Windows 8 with many new and awesome features. We also know that Windows 8 would prompt the users via notification when the update is available whether as preview or final RTM version. Although update would be free for all Windows 8 and Windows RT users but, you will to re-install all your apps after upgrade to Windows 8.1.
ZDNet reports that Microsoft detailed the upgrade method of Windows 8.1 from Windows 8 during the TechEd conference. When the users decided to install the update from Windows Store on their Windows 8/RT device, the download will begin and once installed, you will have to re-install all your desktop and Modern apps again from Store or from installation source(s).
How the update will effect Windows 8 (x86) and Windows RT (Windows 8 on ARM)?
It seems that all versions of Windows 8 i.e. Windows 8 x86 and Windows RT would need to re-install the apps.
Windows 8 (x86): Windows 8 on x86 devices will need to re-install all the modern and desktops apps. Modern apps are available for download through Windows Store while the desktop apps can be installed via the provided installation source.
Windows RT: Users with Windows RT would only need to re-install the Modern apps from Windows Store since, the desktop apps can’t be installed on Windows RT. But, Office 2013 apps would remain there as they come pre-installed in Windows 8 and 8.1 would also include Outlook 2013 as pre-installed app.
Will the Windows 8 apps run in Windows 8.1?
You might be wondering whether the Windows 8 apps will work with Windows 8.1 or not? The answer ‘yes’. All the apps whether desktop or Modern-UI would be compatible with Windows 8.1 which can be installed on Windows 8.
To which version of Windows 8.1 does the re-install method apply?
You would need to re-install the apps in your Windows RT or Windows x86 devices after upgrading to Windows 8.1. This rule of re-installation of all apps would apply to the Preview which is scheduled to be released later this month on June 26 and upgrade to the final RTM (release to manufacturing) version directly from Windows 8/RT would save your apps, settings and customization so, you might want to think before installing Windows 8.1 Preview since, it will remove all your apps.
Note: This method will also apply to pre-installed apps of Windows 8 like the Mail, People, Calendar, Messaging, Travel, Bing Search, Sports, Weather, Photos, Games and SkyDrive etc while upgrading to preview.
Personal data and Settings/Personalization would be preserved
Although, the apps would be removed from Windows 8.1 but, the upgrade process will save your data, settings and personalization and it would be there when you finish the upgrade to Windows 8.1