Steve: Thanks for the suggestion. I checked the firewall settings, and they were okay. Briefly, I disabled the firewall. Even then I was NOT able to ping the new machine from the old ones. I must be in that 0.01% where it isn't a firewall problem.

Ed

99.99% of the time this problem is caused by an improperly configured firewall. On computers running Windows XP with SP2, make sure that the Windows XP firewall has File and Printer Sharing checked off on the Exceptions tab. If you are running any third party firewalls, like those provided by such programs as Zone Alarm, Norton Internet Security, or McAfee Security Suite, make sure they are configured to allow local network traffic.

Steve

Have you rebooted the two older PCs since you attached the new one to the network?

egwiggi,

Which firewall did you disable.  All new Dell computers ship with a security suite.  Which one is currently shipping I don't know.  I am still willing to be that it is a firewall that is blocking access.

Steve

Steve: Thanks! You were right! I had disabled the Windows XP firewall, but it was the McAfee Security Suite's firewall that was causing the problem. I'm adjusting its settings now, but I've already been able to ping the new computer for the first time. Your help is much appreciated.

Ed