Welcome to forums.
Please describe each PC in detail, CPU, OS etc. Does each PC have a network card.
Once you have all of this information
Read this
1) Go to BestBuy or Staples or Comp-USA and purchase a Linksys router. I am partial to Linksys though other brands are also good. If you are connecting more than one computer you will need an additional cat-5e patch cable. If you have XP or 2000 and a certain modem, you will need to contact verizon to take the modem out of bridge mode.
2) Turn off all computers.
3) Turn off Cable modem.
4) Connect the ethernet cable provided with the cable modem to the WAN or internet port on the router and the ethernet port on the back of the modem.
5) Connect the ethernet cable provided with the router (usually blue) to the ethernet port on the PC and any one of the four ports on the linksys router.
6) Turn on the Cable modem and wait for the Power light the ready light and the Link/ethernet light to be lit solid.
7) Turn on the router. Wait for the LAN and WAN lights to be solid green. Red lights that stay on are bad sign.
8) Turn on the PC. When you get to the desktop, confirm the router is acting as a DHCP server.
A) If you have Windows 9X or ME: Start--> Run--> WINIPCFG.
Select your NIC from the pull down menu and check to see
What the IP address is. It should be 192.168.1.100
B) If you have Windows XP or Windows 2000. Go to the
Command Prompt and type IPCONFIG. Check the IP
address and again it should be 192.168.1.100
9) Click on internet explorer or Firefox. It will not work, do not be alarmed. Click the stop button as soon as possible.
10) In the browser address bar type
http://192.168.1.1 and press enter. You will be presented with the login for the router firmware. Leave the username blank and the password is admin in lower case. Once you are up and running, you can go back into the router firmware and change the password.
11) Now comes the dicey part. Depending on the version of firmware (the age of the router) where you put the information will vary. You will look for a pull down menu that usually begins with obtain IP address automatically or a choice of radio buttons. Set the local DHCP server button to enable
12) Re-start the browser and your on line.
13) For any other PC you want to bring on line, just make sure the the NIC 's on the PC's are set to obtain an IP address automatically. and once your plug it into the router your on line and ready to go.
If you want me to talk you through this on the phone, please let me know and I would be happy to do it.
If you've never used the on-board NIC before, it might not be setup correctly. Go into device manager and make sure there are no yellow ! associated with the NIC.
You will need a cat-5 or cat-5e patch cable to attach the PC's to the router. It should not be a patch cable