I've had Ubuntu installed for a few days now and my windows 7 boot. My ethernet port was working fine yesterday and there hadn't been any problems since the installation of ubuntu. I switched to ubuntu yesterday after being on windows 7 and I wasn't connected to a network. So I checked the connection, everything was plugged in. I thought maybe it was an ubuntu problem and switched back to windows. Nothing. It wasn't showing a cable plugged in. So I fired up my laptop to see if I could connect to the network. My laptop had no problems connecting to the network.
In Windows (XP -- you may have to improvise for Win7) go Settings, Control Panel, System, Hardware, Device Manager and see if the Network Adapter is listed or yellow flagged as faulty. If so try Updating the driver.
Also have look in the BIOS screens to see if there's anything relevant that might be causing a problem.
Operating Systems don't usually kill hardware, lack of driver may make it look that way.
I checked the device manager before, windows shows the adapter as working correctly, and I checked the bios made sure some key setting weren't disabled. Everything shows the adapter should be working but it just isn't.