Barry, thanks for your suggestion. The switch is autosensing, and I have no other dhcp server running in the same lan. In fact I just found another possibility that may be related to my problem. One of the three failed PCs is now working. After doing some trial (and error), I realized those three have similar board architecture, that the PCI and ISA slots are on separate board from the main board. The board that contains the slots is connected to main board by a big long slot. I am still working on the rest two (a HP Vectra and a Compaq Deskpro). I have tried to break them apart and clean them but still cannot get the same result. Anybody has the same experience? Fajar.