LAN troubleshooting

i connected 4 computers through cat5 cable for internet accessing with ADSL router siemens speed stream.all computers are browsing internet very good except 1. it is showing LAN connectivity but not doing internet browsing. i changed the cable also but no browsing at all. after i format the operating system also and i changed the network card also but still it is not browsing internet.even if u give manual ip address but nothing , can somebody help me and tell me what can be the cause of not browsing.