This is an annoying issue, I just downloaded the ISO from Microsoft and had to face the impossibility to activate it…
“Windows isn’t activated”
Error Code : 0x8007007B, the filename, directory name, or volume label syntax is incorrect.
The pre register product key is not good and you basically need to change it using the following command (using administrator privilege”
Open a command prompt window
slmgr /ipk HGTY3-JVFJH-3B5VD-WZR8D-JDGR8 (Your own product key of course)
The old product key will be replaced with the new one and Windows 8 RTM will be activated automatically.