HELP! (AVG Antivirus Free Version)

[AlfMaster]

I'm not an extremely tech-savvy person, so I need some help with my new virus protection, recomended by a friend. It's AVG Antivirus Free Version, and when I try to start it, it gives me the message "Enter the DataCenter connection string (http or other DataCenter specification)". Then there's a place to enter it and an "OK" and "Cancel" button. Please, tell me what this is or reccomend another free virus protection.

Thanks!