Troublesome Computer

Hi I’m having an internet connectivity problem with a clients computer.It uses Windows XP in a domain environment with a locally installed antivirus (AVG retail which is expired)and the usual xp firewall.

I am unable to browse to any websites.I’ve tried 2 browsers ..explorer and firefox…..I can ping the FQDN and the ip of the websites but still cannot browse to it.Could it be a port that is being blocked somehow?Or perhaps a virus?