Computer not recognizing ethernet connection

I have a Dell Inspiron 1545 with Windows 7.  I am trying to connect to my school's network using an ethernet cable.  My computer is not recognizing that a cable is plugged in.  An IT guy came by to check the connection in the room.  His computer was able to connect to it (using both his network cable and also mine), so the problem is not with the cable or the network.  He suggested I take the computer in to the IT dept for them to see if they can figure it out, but before I do that, I wanted to see if anyone had any suggestions for what might be wrong.  Thanks in advance!