Symptoms
Thunderbolt devices are not recognized when you start up in Windows 8 after upgrading from Windows 7 to Windows 8.
Resolution
Disable the Windows 8 Fast Boot feature to allow Thunderbolt devices to be recognized.
1.Start up in Windows.
2.Position your mouse cursor in the upper-right or lower-right corner of your screen to activate the Charms bar.
3.Click on the Settings icon.
4.Click Control Panel.
5.Choose "Hardware and Sound."
6.Under Power Options, choose "Change what the power buttons do."
7.Under "Shutdown settings," remove the checkmark from "Turn on fast startup