Same issue here with Windows Technical Preview. The latest Intel HD Graphics (3960) refuses to install with either the Setup executable or manually. Windows update also lists this driver as available for installation, but after downloading reports an error message that the update failed.
I was able to manually install the Intel HD Graphics drivers by:
- Deleting the reference to Threshold in the configuration file that prevented installation with Windows Technical Preview
- Modifying the first line in the Windows 8.1 setup section header to [IntelGfx.NTamd64.6.4]
- Restarting in Windows Troubleshoot mode to allow installation of drivers not digitally signed