Hi thanks for giving me this chance. recently i changed my operating system from windows 7 to windows xp. But then I spent aboout a week without an antivirus. then I got norton internet security 2011 setup which i stored it on the unformatted partition. then i tried to install it but when i run the setup simply nothing comes. I tried another antivirus programs like avg but after installation i get error message that i cannot access the file. I think a virus has attacked my computer. please help me my pc is in great danger. And also some other programs show me the same error.