Hi,

You may follow the options below to determine the cause of this issue:

1. The network cable may be loose or unplugged. To resolve this issue, verify that the network cable is plugged in securely to the correct locations on the computer and on the router/modem.

2. The network cable is defective or damaged. Examine the cable for breaks, for tears in the outer covering, or for damaged connectors. Test with a good known network cable.

3. Ensure that the network cable is connected to the correct port on the network device.

4. You may change the value for the Media Type property on the network adapter:

      a) Click Start, click Run, type ncpa.cpl, and then click OK.
      b) Right-click Local Area Connection, and then click Properties.
      c) On the General tab, click Configure.
      d) In the resulting dialog box, click the Advanced tab.
      e) In the Property list, click Media Type or Link Speed & Duplex or something similar
           If these properties do not appear, look for a property that has the values Duplex and Half-Duplex.
      f) Click a specific bandwidth in the Value list, and then click OK.
     g) Close the Network Connections dialog box.
     h) Test the network connection.

As for the Dell laptop D620, please confirm if you installed the ethernet drivers from the Dell's support site after performing the Operating System Reinstallation.If yes check in Device Manager for any bangs.(Refer to the picture below)

I would also recommend you to check the status of Ethernet Adapter in Device Manager for the other 2 systems.

Please reply with the findings.

Thanks and Regards
Vishal S
#iworkfordell