..... For some time now I have been attempting without success to install macOS High Sierra Public Beta on my late 2009 21.5" iMac. Each time the installer was throwing up an error verifying firmware
message. Probably no great surprise the amount of tinkering around it has had (Intel Core 2 Duo CPU upgrade from 3.06GHz to 3.33GHz, maxed out 16gb RAM and two 1TB Seagate SSHD's) not exactly Apple specification
Plenty of hair pulling and frustration I thought I would give it another bash but using a very
1) Installed macOS High Sierra Public Beta in a virtual environment using VMware Fusion 8.5
2) Once installed shut down the macOS High Sierra Public Beta virtual machine.
3) Mounted the virtual image using Paragon VMDK Mounter.
4) Cloned the mounted image to a physical partition using Carbon Copy Cloner 4
Viola IT WORKED