I'm using McAfee Security Center though only the Firewall. I'm happy with just their firewall, but now that the program has "expired" I keep getting these very annoying messages, both prompting me to update and also the "renewal required" message. Does anyone know how to disable these messages? I've already turned-off updating and error reporting in the program but that doesn't seem to help.

Since the program's subscription has expired, you will have to renew it. I would suggest removing McAfee Security Center and download the free version of ZoneAlarm from:

http://www.zonealarm.com/security/en-us/zonealarm-pc-security-free-firewall.htm