After I put in that post I decided that I might as well upgrade to Windows 11.
I've now completed that and I've checked - I now have Windows 11 Pro Version 23H2.
But I still the same error when try to run the installer.
Any ideas?
Also, the machine is HP ProDesk 600 with 238G storage, 8G RAM, 128M Intel UHD Graphics 630
and CPU is i5-9500 @ 3GHZ.