DM and Lsdmeasap,
I've now flashed the new BIOS. I'd just like to say a big thank-you to you both for your assistance.
Yup, I put the BIOS file on to a small-capacity USB memory stick. And I acted on your advice about those particular USB BIOS settings and 'Keep DMI Data' when it came up.
One thing that others might need to watch out for is that the downloaded compressed BIOS file, and other downloadable files, will have a security lock on them, under Windows XP. So, before using them, it's best to right-click on the downloaded file, select Properties, and then unblock the security lock. This may not actually affect anything outside of Windows but, all the same, it seems a sensible thing to do, especially if you're about to flash a new BIOS.
I was a bit thrown when Q-Flash found the USB drive but appeared to say '0 File(s) Found', but it was simply a matter of pressing Enter a further time, to drop one further step down the menu. The checksum it reported was CD00.
A couple of queries have since arisen: In the BIOS, have you any idea what "Onboard LAN Boot ROM" is all about? I've set it to Disabled. And what happens (other than the obvious) if you set "Delay for HDD" to a certain period? Does the machine spend that time checking and counting the RAM, and showing that on the screen? I've disabled the logo screen, BTW. On my old machine, there was no such delay setting in its BIOS but the machine would start the boot-up by first counting and checking the RAM. After it finished that, the bootup into the OS would take place. You could cut short the time it spent doing the memory check by pressing the Esc key. Does this Gigabyte BIOS work in the same way? Although we all like to have the system boot up as quickly as possible, I've hitherto found it useful sometimes to allow the memory checking to take place, as it gives you a proper opportunity to read all of the data on the screen.