Windows – Unable to install Boot Camp 6 Update for Windows 10 due an invalid signature

I'm having the exact same problem. I tried holding the option key when rebooting to see if I could boot from the USB key but I could not find a way to do this, so I installed rEFIt (then rebooted twice!) and THEN plugged in the USB key and the next time I rebooted it did show up as an option to boot from the USB key.

I tried that and the windows installer loaded and it found the new bootcamp FAT32 partition. It said I couldn't install to the bootcamp partition because it requires NTFS.

This SuperUser post suggests "simply format the partition using the Windows installer's built-in utility (in other words, as part of the installation process)" so I did that continued with the install and everything works fine!

I got it (at least the parts in my question) working:

• Reboot
• Reboot again
• Run boot camp and remove old installation (this time it worked)
• Reboot
• Run boot camp and start Windows installation
• At the choose partition screen, choose the boot camp partition, select Drive options, and then select Format.

I wonder why it worked this time, but not the first. Now I get a error message of corrupt files however. Guess I have to download the DVD image from MSDNAA again.