Trying to Reinstall windows 10 on a non-bootable computer

Have an open thread where computer will not boot due to Inaccessible_Boot_Device. Tried many things but nothing worked. Thus, now downloaded a Windows 10 64-bit iso file - burned it to disk. Now trying to due a custom install with this disk.
However; it says I cannot install system on any of the partitions as they are GPT.
Drives are:
1 Drive 0 Partition 1 ESP - drive is GPT, thus cannot install. Type System - 500 Mb
2. Drives 0 Partition 2 and 3 are reserved OEM and MSR
3. Drive 0 partition 4: WINRETOOLS - type recovery
4 Drive 0 Partition 5: OS - 1845.5 GB - Primary Drive - Windows cannot be installed as it is a GPT partition style - THIS IS WHERE I HAD PLANNED ON INSTALLING WINDOWS 10
5. Drive 0 Partitions 6,7,8 are recovery drives
Drive 1 Partition 1: 128MB (MSR Reserved). Again GPT type
6. Drive 1 Partition 2: New Volume (this is empty) - 29.7 Gig. I believe this is the SSD attached to the HHD - type Primary. Again GPT

NOW WHAT: Did I download the wrong iso file, or where and how should I get past this problem. What would happen if I format? But which one. Don't yet want to do format without advice as once I do I will not be able to boot Via Safe Mode anymore.

Help is needed.