A DNS error is rarely caused by hardware. I'd look to software issues. Another oversight is that many will not load current BIOS and drivers when they install a Windows OS. Be sure its current.
I just built an amd athlon 2400
asus a7n8x-x motherboard
256 ddr 400 ram
40 gig wd harddrive
onboard nvidia network card
I can not get it to connect to my dsl internet with my linksys router. The router lights show it sees it and the other 2 computers are on line. I checked the network settings and they seem right, but i get a dns error when i try to go online. please help