he has a wireless card. It sounds like it's a 802.11 G.
Does he have a wireless router?
If so, what brand and model number.
The setup would be
Earthlink DSL > wireless router > Wired or wireless connection.
It should NOT interfere with the connection unless the wireless router is on a channel near the neighbors. The wireless connection can be interfered with if you have a 2.5 gh portable phone, the wireless kind that you use in the home. You can buy the 5 gh type for the home and there is no interference. Also before he decides what channel to use, have him look at the channels the neighbors are using.
Hope this helps.
Rick
Hello forum.
My nephew recently bought a laptop and has wireless connection installed. He is hesitant to get it going. Where he lived before he and his roomie could be on the Internet at the same time because either the dsl or the wireless connection would drop off. I have Earthlink DSL and he is sure it would interfere with my connection.
I'm on a MAC Powerpc with plenty of memory and harddrive space as I use two external harddrives.
OSX
Earthlink DSL
He has Windows XP
A Turbo Wmm 2.4 GHz OFDM 54 MBps IEEE 802-11G Wireless LAN PC CARD
Is this problem a common thing and is there anything he can do? He hasn't set anything up yet.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic