Ah - the backup killed it totally! After a whole rest of the day yesterday, it turned out to be the motherboard, but a friend had given me his Athlon 2000 and board, and after the rest of the rest of yesterday (up to 2 am) I had that nearly right but no PCI bus and the drivers seemingly missing.

This morning got me nowhere - but my optical drives disappeared in Windoze (still there in the BIOS).

Just after a sandwich I had decided to format C again (!) when I hit the wrong button, did an over-the-top by mistake, and it found the network and the optical drives so apart from a few bits of installation I'm back!!