I have a homebuilt computer with a GA-Z68MA-D2H-B3 motherboard with a Realtek RTL8111E LAN chip. Ethernet was working fine in Windows 7 until I reinstalled this OS, but now it's stopped, while still working in other OSes. I've tried reinstalling drivers from both the Gigabyte and Realtek sites to no avail; I've also plugged in and installed an Asus USB-N13 wifi dongle and this doesn't work oddly. How can I diagnose and fix this issue?

In 'Network and Sharing Center' says "The account specified for this service is different from the account specified for other services running in the same process" under the heading 'Unknown'. Following the advice at http://www.sevenforums.com/network-sharing/130159-dependency-service-group-failed-start.html#post1122627 I've gone to 'Control Panel=> Admin Tools=> Services' and ensured the services listed at that URL are started (one - IIRC 'Come+ Event System' refused to start as user 'Local services' so I've had to set it to log on with the 'Local system account'... I suspect this may be part of the problem).