Are you using the DG834 or DG834G? It's just that the DG834 doesn't have wireless.
Anyway possible typos aside...In the wireless settings in the router is the wireless function turned on? (I know it's a bit obvious but you'd be surprised how many people, myself included, get tripped up by things like that!) are the security settings turned on? If the security settings areon then turn them off until you get the connection up and running set them up after, settings like trusted PC's only or WEP/WPA settings should be unticked.
Give the access point on your router a SSID name and make sure it's ticked to broadcast. On your Son's laptop make sure the wireless is turned on and try searching for the SSID name. If you have XP SP2 installed it has a useful wizard to help with this.
If you are still having no joy is there anyone else with a wireless connection that you could use to check both the router and your Son's laptop are functioning correctly?
That's all the advice I have for now as I have to go. Hope it helps.