Hi,
You may need to know the following when you upgrade to windows 8.1 enterprise:
Upgrading from Windows 8 Enterprise to Windows 8.1 Enterprise:
Download your Windows 8.1 Enterprise media from the Volume Licensing Service Center (VLSC). Please note that Windows 8.1 Enterprise cannot be updated from the Windows Store; it can only updated using media obtained from the VLSC. Use this media to either:
Perform an in-place update of existing Windows 8 Enterprise installations.
Refresh existing computers using MDT 2013 or System Center 2012 R2 Configuration Manager*, or burn the media to a DVD or copy to a USB key for simple installation.
Windows 8.1 General Availability: The IT Pro Perspective
http://blogs.windows.com/windows/b/springboard/archive/2013/10/18/windows-8-1-general-availability-the-it-pro-perspective.aspx