I have a Dell Dimension 9200 with an 82566DC (Gigabit) LAN port on motherboard. O/S is now Win7 64-bit SP1 fully patched. Previously was on Vista.
The only way I can get it to connect reliably to my 100Mbps router is by setting a fixed IP address, gateway and DNS.
If I set it to utilise DHCP, Windows thinks the network cable is not connected. Clearly the cable is connecting, because lights blink when the cable is connected AND it works perfectly with a fixed IP address.
I have loaded the latest PROWin64 drivers from the Intel website and tried the driver supplied from the Dell website, but fixed IP seems to be the only reliable way of making it work.