Cannot connect to internet

Hello Forum and i am new here.
This problem has never happened before and i am at wits end.
I am operating 2 desk top macs literally right next to one another.
Mac#1-Mac OSX 10.6.8---turns on and i can use everything, it just wont connect to the net.
Mac#2-Mac OSX 10.6.8--everything works fine including internet
One connects fine to the internet, the other will NOT connect either by wireless or ethernet cable.
I have tried troubleshooting myself but nothing works!
The Network icon tells me everything is fine--airport and ethernet connected and strong signal----but it won't connect--says that the server where this page is located isn't responding.(google--works like a snap on the other Mac-very confusing)
Does anyone have an idea of what to do?
Has this happened to you?

 

On computer #1, connect ethernet cable.

In System Preferences -> Network under the ethernet connection, what Configure IPv4 setting is chosen?

If you also click Advanced button, what IP numbers are shown?

 

Thx for your help.
Info on computer which wont work is--
For ethernet connection it shows Using DHCP
ip address is 192.168.15 subnet mask is 255.255.255.0 router 192.168.15.1

The mac which works shows:
Using DHCP also and IPv4 address of 96.24.164.13.....subnet mask 255.255.240.0 router 96.24.160.1
I tried to change the non-working mac's info to match the working macs info but could not do it---too advanced for me
Don't know what other details to post---kind of driving me crazy especially because i am hard wired to a router that works---Clear Communications WiFiRSU_cc
Thanks for your help!

 

Have you modified the default settings on the the router?

From the info you presented, it appears that the router is connecting directly to your ISP for the first computer but serving IPs for the second.

If you turn off the working computer and restart the second one that wasn't working, does the info change?
(This is all with WiFi off for now)

 

don';t know anything about default seetings but i have an appointment with the mac people at the genius bar in 30 mins and will be back witth a post---thanks so much

 

bottom line is harddrive was and has crashed....it had locked up on me 3 days ago and then i let it sit and could get back into the system.....so when i was in the system i could not access the internet....but the mac store people are very cool about diagnosis for free and they could tell that it was soon to be "toast".....so now i dropped it off at a local computer guy who will install a new hard drive----they use western somebodys drives....ever heard of them?> Mucho thanks for your help on this one