I am absolutely horrified at this attempt to force me to upgrade to 8.1...
I dunno about being forced to install Win8.1 but - assuming KB2871389 & KB2973544 have been installed - have you read http://support.microsoft.com/kb/2973544?
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This article describes an update that enables Windows RT to update to Windows RT 8.1 and that enables Window 8 to update to Windows 8.1...If you have Automatic Updates enabled on a computer that is running Windows RT or Windows 8 and that has update KB2871389 installed, [installing KB2073544] can automatically start the update process to...Windows 8.1.
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Note that Win8.1 must be installed by 12 January 2016 or the computer will not be offered any further updates.