My ethernet connections keeps saying unplugge

Hello, i got a used compaq presario and it has via rhine ii faster ethernet adaptor, and when i hook up my dsl saying its unplugged, i've tried everything to pc doctor says its turned off and not connected. ??? i've disabled and enabled it , changed ethernet cords, system restore. and nothing helps. and when the ethernet cord is plugged in there is no light in the back what does that mean? and what can i do to fix this. please help .