same ip on two computers?

We have 4 computers in our home; 2 pcs and 2 laps. The 2 laptops work find on our network, the 2 pcs don't. Recently, I've been getting a message on the 2 pcs- "Windows System Error- There is an ip address conflict with another system on the network" How do I go about fixing this? I contacted my internet provide-comcast, but they told me the problem is with the router. My daughter took out the connection and reconnected the router and that is when the problem started. You have to turn one pc off, to use the internet on the other and vice versa. I'm just not sure how I go about resetting so the computers have two different ips, I mean I thought they did already but something has gotten messed up.

hi, your external ip will be the same. your internal ip is assigned by the router and will be different: 192.168.2.XXX (100-254) in xp go to start>run then type in the box cmd when a dos window opens type at the curser ipconfig this will display the internal ip address of that computer. i would try turning off your modem then the router. then power them back up. then reboot the computers to force a new ip

I tried what you suggested. I rebooted the two pcs, router and modem. When I started PC #1 it was fine and PC #2 was fine. I signed on with PC #2 and as soon as I did, it kicked PC #1 off and I got the error message again. I tried what you suggested and got the following- PC #1- Connection-specific DNS Suffix . : Belkin IP Address. . . . . . . . . . . . : 192.168.2.6 Subnet Mask . . . . . . . . . . . : 255.255.255.0 Default Gateway . . . . . . . . . : 192.168.2.1 PPP adapter {6098CEA7-3F32-49A6-AC77-B147691ABAC9}: Connection-specific DNS Suffix . : IP Address. . . . . . . . . . . . : [removed] Subnet Mask . . . . . . . . . . . : 255.255.255.255 Default Gateway . . . . . . . . . : PC#2- Ethernet Adapater Wireless Network IP Address. . . . . . . . . . . . : 0.0.0.0 Subnet Mask . . . . . . . . . . . : 0.0.0.0 Default Gateway . . . . . . . . . : 0.0.0.0

Ugh. I give up for now. I called the company with our router. Spent 45 minutes on the phone and decided that it was the network card on PC#2. Every suggestion he tried didnt work. With PC #1 it just had one connection but with PC#2 there were two options LAN and the wireless adapater[not the same company as the router]. Because after the power outage, when my daughter restarted the router they said that the other wireless cards were reconnected but PC #2 didn't and theyre not connected anymore=the settings are the old ones and that is why it is coming up with the same ip. So I have to call tech support for the company of the wireless card with PC#2.

PPP adapter {6098CEA7-3F32-49A6-AC77-B147691ABAC9}:

this maybe some of the problem here, you should probably set this to be on the modem. You can do that on your modem settings which you should be able to reach by typing http://192.168.0.1 into the url address bar of your browser.
Also I would set computer 1 and 2 to obtain ip automatically.