Really odd problems any ideas.
Machine was mothballed for about 9 months whilst decorating. After it was plugged back in the PCI Gig NIC cards refused to work. Nice "!" in the hardware folder against the card under system. Reseated it, move the slot it used reinstalled drivers no luck. XP found it and drivers tried to install but never came up with the "Your hardware is installed message".
Bought a new PCI slot NIC, different maufacturer and chip provider and the same is happening. Again switched PCI slots but no change, uninstalled and reinstalled still the same problem.
1394 card in another PCI slot is working fine.
Welcome ideas