Error installing Windows 10 64 bit under El Capitan's Boot Camp It gets to the point of rebooting into Windows but then "upgrade" says "Booted from install media, reboot under Windows" and "Install Windows Only" says the BOOTCAMP partition is incompatible because it's not NTFS. If I reformat the partition, it then says "Unable to create or locate partition see SETUP.LOG" and I can't find SETUP.LOG (in any case - upper, lower, or mixed)

What do i do now?
You must do everything (install, partition, uninstall, repartition, delete partition) with BootcampAssistant, nothing else.
Start bootcampAssistant and delete the windows partition.
restart the mac. Then do everything agian, with BootcampAssistant.