I believe that I installed a firewall months ago, but now I can't remember the name of it or if I even went through with it. How can I check to see if one is on my computer? I believe it is because there are certain ads that will not display. I want to remove it.

If you have a security suite it will probably be rooled up in it. What is your antivirus?

I've used Norton and McAfeee, but now I don't have one. I had just done scans every now and then, but I only visit the same sites now, so I hadn't kept anti-virus software up.

Have you checked dd/remove programs to see if you can reconize the firewall? Here are a list of free firewalls. Could it be one of them?

Zone Alarm Free for Personal Use
SyGate Personal Free Edition (I personally use)
OutPost Firewall Free
Jetico Personal Free
Kerio Free Personal Firewall