Should I choose Upgrade or Custom installation?
Choose Upgrade if you:
•	Want to keep Windows settings, some server roles and local files in Windows Server 2012 R2. Not all Windows settings and applications will be moved. If you’re upgrading to Windows Server 2012 R2, no applications are kept. 
Note: You can't use this version of setup for upgrading to Windows 8.1. If you want to upgrade to Windows 8.1, start setup.exe from the root of your installation media.
Choose Custom installation if you:
•	Want to delete everything on your PC. 
•	Want to install Windows 8.1 or Windows Server 2012 R2 on a separate drive to multiboot into other operating systems.
•	Don’t have an operating system installed on your PC.
•	Aren’t able to upgrade from the version of Windows that’s already installed on your PC.
If you choose Upgrade, make sure that you do the following before you continue:
•	Back up your files to an external hard drive, DVD or CD, USB flash drive or network folder.
•	Find the installation media and installers for the applications that will work and need to be reinstalled in Windows 8.1 or Windows Server 2012 R2.
•	If you use a fingerprint reader or another biometric device to sign in to your PC, make sure you write down your password. You’ll have to type your username and password the first time you sign in to Windows 8.1 or Windows Server 2012 R2.
Note: Your personal files will be moved to the windows.old folder.