da1nonly
There are a few things that will disable Windows firewall and not allow you to turn it on. If you are running another firewall such as Norton if you selected to allow Norton to disable Windows Firewall when you install it will prevent you from turning it on.
Another thing that will prevent you is not quite so pleasant. There are several viruses running around out there that will disable the Windows firewall. These viruses will also disable your antiviruse's ability to detect them. Just because your antivirus did not detect a virus does not mean there isn't one there.
I would suggest you do a on line scan just to make sure. There are a couple of links below to on line virus scans.
http://security.symantec.com/sscv6/d...d=ie&venid=sym http://housecall.trendmicro.com/ http://www.pandasoftware.com/products/activescan.htm