I've found two problems when trying to install W10 that have nothing to do per se with Windows.
1) If you have any SD cards in your system - remove them while doing initial Windows install -- they can be put back into the system after install.
2) More than 4 HDD's or 4 Partitions -- Windows also goes Bonkers with "Cannot install Windows to this partition.
Another possible problem -- If you've got some sort of RAID controller and the driver isn't loaded ad Windows install time.
Disable secure boot too - it's just a HASSLE. You can still use UEFI if you want to - then ensure boot HDD is GPT formatted.