How can I fix my internet problem!?

I think I have a virus that is keeping me from accessing the internet. I downloaded a program that has been said to have a virus and Norton told me it did but I decided to download it anyway. Now, one day I try to open Firefox and I get "Page Load Error", like I lost connection or something. I have a wired connection, though. I have run many scans with Norton 360 and Spyware Terminator, but they found nothing. 'Network Connections' says there's nothing wrong with my connection either. I am running XP if that helps. Please help me!