Microsoft documentation has worried a lot of Windows 8 users because it says that its not possible to upgrade from Windows 8.1 Preview to Windows 8.1 RTM. But wallop the worries now because we will tell you the other way around to safely upgrade to Windows 8.1 RTM from Windows 8.1 Preview without loosing your files, apps and data.
Lets get started, follow these steps:
1) Open the "Windows_8.1_EN-US_x64.ISO" or any other Windows 8.1 RTM ISO with any famous ISO explorer like Daemon Tools, PowerISO, Ultra ISO
2) Browse through the folder \sources\
3) Open "cvversion.ini" file using Notepad or any other text editor
The .ini file will look like this
4) Change the "MinClient" and "MinServer" version from "9458.0" to "9431.0" and Save "cvversion.ini". This value is the OS version you're upgrading to.
5) Save the ISO file after making changes
6) Write the ISO to DVD or removable media (bootable) and do the installation. You can now safely upgrade to RTM with all apps, settings, files preserved.
What we basically did was rename the RTM version number to Preview version number. All the files and upgrades are intact in the ISO but the installer now believes that it's doing an upgrade of the Preview Version so it lets you keep the apps and user files. Wasn't it a piece of cake? [via mydigitallife]
In case you're upgrading from Windows 8, read this guide on how to upgrade to windows 8.1 without losing apps.