"Local area connection doesn't have a valid IP configuration" on Windows 7; Why?

I recently upgraded my desktop computer from Windows XP SP3 to Windows 7 RC 7100. Prior to the upgrade, my internet connection was perfectly fine. Now when I try connecting to the internet on Win. 7, I get said error from the troubleshooter.

I have no modem or router, for I live in a university-affiliated apartment where one can connect a computer directly to a wall jack via ethernet. I was considering buying one but it seems silly to if Win. XP worked flawlessly without it before.

The connection comes up as a public, unidentified network.

So far I’ve tried installing the network drivers for the mobo, using the Windows troubleshooter countless times, changing the network from public to home, changing the ethernet cable, and googling to see if anyone has had the same problem and found a solution. No results.

Any help is greatly, greatly appreciated.