Installing Windows 10 "We couldn't create a new partition."
Solution 1:
I have found a fairly simple solution. (This if for people who are installing via USB)
Go into your bios and set the HDD that you want to install as the very first boot device. Save and restart.
Manually access your boot loader when bios starts. From here select your USB to boot with.
Proceed normally with the install.
It seems that the partition manager in the windows installation gets confused when when it detects a USB that has a higher boot priority then the HDD you're installing on. It thinks the USB is the system partition. By setting the HDD to the first booting device, it no longer looks at the USB as a boot device.
This would also explain why the remove USB key while creating the partitions work. By removing the USB, it no longer sees it and so it skips to the next bootable device to look for the windows system partition. When it doesn't find one, it will now device to create it on its own.
Hope this helps some of you. It took a few hours of sleep out of mine.