Windows 7: Computer Doesn't Detect Ethernet Cable

I recently moved into the dorms of my college and tried connecting my laptop to the internet using an ethernet cable. It worked, so I decided to try and play Xbox Live through the use of the ethernet cable and it did not work. After messing around with it and failing to get it to work for my Xbox 360, the ethernet decided to quit working for my computer as well. The "Local Area Connection" isn't there when the cable is unplugged and only shows up for a second when it it plugged in and disappears. If I click on it fast enough, it shows up with an Error Code 45 after looking at the properties. I have tried typing in ipconnfig /all and the ethernet connection doesn't show up there either. If anyone can help, I'd appreciate it. If you need any more details, just ask.

Interesting note; I tried connecting with a new ethernet cable again (with no success), however, if I click on the local area connection that the ethernet cable creates before it disappears and create a MAC bridge connection with it and my wireless connection, I can get online, with very unstable connectivity. So this method does not work, but I found that doing so actually allows the local area connection to stay shown with the ethernet cable plugged into both my laptop and Xbox 360 with a bridged connection. If I remove the cable, the connection goes away.

Deleted post due to irrelevancy.

I have bought another ethernet cable and it still does not work. I have also bought a USB to Ethernet converter and the connection still does not work.

Went to other forums for help instead since I didn't receive a reply here. Found out my problem.

link speed most likely, is your link speed set to gigbit and the lan you're connecting too only 100mb ? Set the card to auto-negotitation to see if that helps.