Problems With Home Network

i have set up a wireless home network

it was all perfect for a while until the IP's started conflicting, so i reset it all

now i can get full internet and app use on the main PC connected to the modem/router through ethernet

also i can get full access on apps and browsers of a laptop connected to the same wireless network

however my Main desktop upstairs is having problems

steam accesses the network fine, low pings, downloads fine

but no other apps can

even though there is an active internet gateway on the computer,

i can ping IP's from command prompt, but not url's (www.google.com etc.)

im really confused so any help would be really appreciated!

cheers in advance

Barney