The Dell XPS/Dimension 420 desktop system has an integrated wireless Ethernet LAN on the system board and an internal wireless-N card. The computer, which comes with the Windows Vista operating system, can connect to a wireless Internet router without the aid of an external wireless card or adaptor. There are many reasons why the Dell 420 is unable to connect to a wireless router. There may be problems with the router or the Dell is not configured to receive signals from the router.
Double-check the wireless router set-up. Make sure the Ethernet cable from the DSL or cable modem is connected directly into the wireless router WLAN/WAN/Internet port. If the router is connected to another computer, verify that an Ethernet cable is connected into one of the router ports on the rear of the wireless router and the Ethernet port on the computer.
Restart the modem and router. Disconnect both the modem and router from the power source for 10 seconds. Then plug back in the power source. If there is still no Internet connection on the Dell 420, go to the next step to configure the computer to connect to the router.
Connect to the Internet. Select the "Control Panel" from the desktop Start menu. Click on "Network and Internet," and then select "Connect to the Internet." Choose "Broadband" as the Internet type. Follow any additional on-screen prompts. If there is still no Internet connection, make sure the Dell 420 is trying to connect to the correct network.
Select the router. Click on the small network icon in the desktop taskbar. All available networks within range will be listed. Select the network you want to connect to. If prompted for a network key or pass phrase, enter it into the corresponding fields. Press "Connect." If there is still no Internet connection, make sure the modem is communicating with the Dell XPS 420.
Verify that the modem is communicating with the Windows operating system. Select the "Control Panel" from the Start menu on the Windows desktop. Select "Hardware and Sound." Choose "Phone and Modem Options." Select "Modems." Select your modem and hit "Properties Diagnostics Query Modem." Windows will run a few tests to verify whether or not it is able to communicate with the modem. If not, follow the Windows prompts to fix the problem. If there is still no connection, proceed to the next step.
Run the Dell XPS 420 modem diagnostic tool. Select "All Programs" from the desktop Start menu. Choose "Modem Diagnostic Tool." Follow the on-screen prompts to identify and resolve modem issues. If there is still no connection, proceed to Step 7.
Verify that the Dell 420 is receiving the router's Internet protocol address. Enter "run" into the search field on the Start menu. Enter "Cmd" field. Type "ipconfig/all." The IP address should be listed and may be similar to this number: 192.168.1.x. If the IP address starts with a 169, connect the Ethernet cable from the router directly into the Dell and it should be able to pick up the IP address. If there is still no connection, proceed to Step 8.
Ping the router. Enter "Run" in the search field on the desktop Start menu. Enter "Cmd." Type "ping (and the router's IP address)." For example, type "ping 192.168.1.1". Packets will be sent to the router from the Dell 420. Follow any additional prompts.