Have the client share here too? Your post is void of details such as make, model, the story about drivers and more. And that old story about Norton means software titles that expire can play a role here.
Why not let them tell more?
I have a clients computer that will not connect to the internet. Running xp. I installed a new net card and still get the same problems. It tries for a while to get ip address then gets limited or no connectivity. Dsl works fine on another computer. They said it worked fine a few months ago, did a system restore but no good.