OK from the start... my computer was working fine everything was going until my nortons security was expiring it had about 1 day to go so i uninstalled it because i had purchased another anti virus (mcafee internet security 2012) however the thing is it wont let me install, so i tried downloading avg free version however it never let me install and from there i found out that my computer wont let me download most of the time and when it does it says files corrupt further more it also wont let me extract files and wont let me update things like windows defender... if theres anything you guys can do to help il be really greatfull thank you.