Ping problem

Recently purchased Optiplex170L w/integrated NIC, XP Pro w/SP2,

peer to peer 5 XP Pro machines, 3 Prns. all w/static IP addr.

NIC "status" panel shows all ok. Optiplex will ping any other machine on the network,

including prns...gateway, dns, etc.Device Mgr shows no problems.

Problem is:  This machine times out on attempt to ping itself/ net-diag shows a "failed"

connection, Selecting network places, "view netwk computers" produces panel saying

"network not available"

What am I missing??