Hello everyone! Well, I'm back ... sort of.
I swapped over the SCSI card in PCI4 and the soundcard in PCI3, and rebooted. The machine asked for the driver disk for the PCMCIA device (yes!), loaded some stuff from that, and crashed to blue-screen-of-death. Windows wouldn't start at all after that - just gave a message about missing drivers.
I tried to reinstall XP, and it refused. A long night followed...
Many hours later, with some brilliant advice from WCollins, I'm back, with the Win XP config I had before (more or less). I can access the Internet, and my Word, Excel, etc documents are there. Phew! Lots of stuff is temporarily missing, but I have a shrewd idea where it will be...
The cards are back where they were, but instead of all the PCI cards being on IRQ9, they are on several different IRQs, there is no "ACPI Compliant System" and I no longer have a working sound card, second SCSI card (the one for the scanner), PCMCIA adapter, or joystick.
Anyone know how to get the thing back to the "all on IRQ9" setup? That worked, apart from the Jepp card writer, which I've decided is probably faulty.