Connected to network but not getting access to internet

I had a laptop that was connecting properly to the network and getting a valid IP but did not get access to the internet. Manually configuring an IP sometimes let the computer get access for a day, sometimes for a couple minutes and sometimes not at all. Norton Anti-virus did not pick up anything and I could not switch to another AV program to do a proper virus scan. The laptop had the same behaviour on wifi in the office but the internet was working on wifi home. I installed a free firewall which showed hundreds of connections being made to a handful of servers and the connections being started and shut down every few minutes.Eg. there would be 20 connections (a normal amount) one minute and a couple minutes later it would start increasing up to 700+ for a couple minutes then go back down to 20. It was infected and every so often it would try to send something out.

It turns out the office firewall was blocking it when it detected a flood of connections coming from the laptop.The problem was solved by formatting the machine. I had already spent many hours trying to clean it but got fed up of it so formatting was the way to go.