Did you install the chipset driver and Ethernet driver from the support page? In device manager do you see any problems indicated for your Ethernet, and do you actually see the Ethernet device in device manager?
I just finished a fresh clean install of Windows 7. My network is fine because all other devices are given an IPv4 addresses. I've started up with F12 and chose BIOS setup.I chose Load DefaultsIn BIOS > System Configuration > Integrated NIC, 'Enabled w/PXE is active' I don't know much about PCs at all so I could use someone's help There are two LEDs on the integrated Ethernet port, the top one is solid orange and the lower one blinks intermittently in orange. Is this a hardware issue? I did run the diagnostics and no trouble was found. Thanks  
Optiplex 3020 Ethernet not working (Integrated NIC)