I use McAfee as the anti-virus solution and its firewall for protection and monitoring. I have not been using the firewall for a while as it used to make my computer a little slow. Now, when I want to start the firewall because of sudden increased threat of infection, it refuses to do so. It gives me an error saying something like a service was not able to start. How do I make the service start?

To enable the service once again click
on Start | Programs | Control Panel | Administrative Tools | Services. In the Services window that appears, look for the McAfee Firewall service (or the firewall you are using on your computer). Right click on it and select "Start". If it does not start and still gives an error about some dependencies failing to start then right click and select Properties. Click on the Dependencies tab and click on the + sign for the item under This services depends on the following system components.

After you have expanded the list completely, look for services (from bottom of the list to top) with the same name in the main Services window. Enter their properties, make their Startup type automatic and Start the service. Only after you have started all the services that the McAfee Firewall service is dependent on can you start the programs own service. Close the Services window and enable your firewall now.