However, I am back to square one after doing a system restore going back 4 weeks.
Oh dear. Number one rule if you've got a suspected virus. Delete all your system restores, they are no longer trustworthy.
Can you get us a screenshot (or at least a copy/paste of the exact error message) of what the various browsers you are trying show when you try to access links ?
Do any websites work (e.g. BBC ?).
Do you have any secondary systems you can test your broadband on to rule that out ?