In Win8 under Network adapters in Device manager the N-6235 driver appears but there are no 2 Microsoft virtual WIFI miniport drivers listed.
Since nothing has worked to make widi operational, I have now deleted/uninstalled all Intel drivers. The N-6235 driver listed there is the Microsoft driver that came with Win8: 14.8.8.75 dated 12/5/2011. Also, the Bluetooth driver is the Win8 Microsoft built-in one.
I have used Wise Care 365 and CCleaner to get rid of other traces that may linger in the registry and system.
After running the above utilities, I manually deleted all Intel wifi/widi files from the system and all such traces from the registry.
After doing that I installed the Intel wifi, the video 4000, and the Intel widi drivers in that order but no luck. The same platform error appears when the widi installation starts. The wifi and Bluetooth work fine.
After doing that I went back and using the utilities and manually, deleted again all Intel files/traces as described above.
The wifi and Bluetooth work fine with the Win8 built-in drivers.