Basic stuff so apologies in advance in I'm seeming to tell you how to "suck-eggs"... but are you using a Cat 5 connection? - Do you have a hub or are you using a cross-over cable? (or trying to connect through a straight-through cable or thin ethernet?) - What OS are you using? (are they both the same?) - Are you trying to connect to a common Domain? (Does your brother run a network or are they just two stand-alone PC's?) - Are you using the TCP protocol or something else?