How to resolve partition error?

[Windows Central Question]

I have had lots of experience with os installation. For the first time I have hit a wall. I have two HDDs with 4 partitions on 1 and 3 partitions on the other. 1 of the partitions has windows 8.1 installed on it. So i deleted one partition that I did not need from the same drive and got unallocated space using AOMEI Partition Assistant. I created a bootable windows 10 flash drive using rufus. When I get to installation, and try to install windows 10 on the unallocated space, it gives the error, "Windows could not create a new partition or find an existing one. Check setup log files." In fact I get the error on all the partitions. I have read about the DISKPART procedure but as I understand, it will format one of my drives completely, but I do not want to lose the data on my other partitions. I have even tried to install windows 10 directly from windows 8.1 using setup.exe in the flash drive. The installation got stuck at the loop where I choose what to keep-personal files and stuff. I am feeling really frustrated. Solution?