No idea WHY it wouldn't recognise the SATA drive, but by the grace of God, it does now.
Ebuyer.com had some cheap fast memory in, so I bought a second 2Gb - now running 4Gb of CL4 667MHz RAM, but this stuff is rather nice, and runs happily overclocked to 800GHz to 2.0v. The update was originally intended to let me use 'Tiger one' which is MSI's overclocking software. But that started hanging when I tried to use it, so it's uninstalled and any overclocking will be done the conventional way, through the BIOS.
Live and learn.