What's the brand & model of Ur

The socket you see besides the phone jack is either a placeholder for RJ45 (but never built in) or a sliding cover for RJ45 jack. See if you can slide it open.

The Ethernet Adapter you found under Devices may be the software driver required for a 3Com Card. Are you the original owner of this notebook? If not, maybe the owner before you had such a card but never uninstalled the driver.