OK, managed to do clean install (Pro) on formatted drive (no upgrade anything). Earlier failed effort was due to using unetbootin to put win 10 on usb, but it didnt format properly. So clean install works, now to research best way to activate and keep activated.
Hmmm.... I had one Insider 10166 build in a VM, which I managed to "clean install" on and remain activated I set up a new VM with the same hardware specs and tried to do another clean install from scratch but it says the product key is invalid