Unable to turn on Windows Firewall on Windows 7

You could also have been hit with malware that prevents essential security services from starting... either by affecting service dependencies, or by deleting keys in the registry that are needed to start them. If that's what happened, I recommend backing up your data and reinstalling windows, then install active malware protection such as MalwareBytes Anti-Malware - you can turn that into the Pro version, which provides active monitoring and can prevent many malwares from installing. For what it's worth, I have no association with MalwareBytes other than having paid $25 for the pro version myself, over a year ago. Nothing will prevent ALL virus and/or malware infections, but MBAM has stopped quite a few on my laptop since installing it.