You appear to have secure connection failure.
First make sure that your date/time are correct, including your time zone. Quite a few people find they have their times zone incorrect although the time looks OK.
If that's not it, go to internet options advanced tab and uncheck "Check for server certificate revocation". It should normally be checked but if often seems to cause this problem. You need to restart iTunes for it to take effect.
If that doesn't work, as a bit of a long shot, try this article about something slightly different.
http://support.apple.com/kb/TS1593?viewlocale=en_US
If that doesn't work what security software are you using and have you ever had Norton on your PC EVEN if you have uninsatlled it?