Thanks for the reply, pip22. It turned out to be a bit more complicated than that - the BIOS has sufficient USB support (because I can boot from the installation CD in the USB CD drive), but Win2000 installation is unintelligent enough (or perhaps just old enough) to insist on trying to use its own non-existent USB CD support on the first reboot. So I could read the CD the first time round but there was no supported device to reboot from.
After hunting for USB-CD support that would work in DOS, I finally solved the issue by taking the hard disk out of the notebook, hooking it up to a computer with an internal CD that could be booted in Win98, copying the Win2000 installation folder to the hard disk then putting the disk back in the notebook and installing Win2000 from the hard disk. Sounds crazy, but it in fact worked painlessly.
Case closed.