Actually, i would suggest that you keep the Windows Firewall Service running even if you do not use Windows Firewall as i have found disabling it will interfere with sharing options, such as printer sharing on your network. If you disable Windows Firewall Service you will be unable to share printers instead you will just receive error messages and it will probably affect other areas too.

This is what Microscoft have to say…

Do not disable Windows Firewall by stopping the service. Instead, use one of the preceding procedures (or an equivalent Group Policy setting) to turn the firewall off. If you turn off the Windows Firewall with Advanced Security service, you lose other benefits provided by the service, such as the ability to use Internet Protocol security (IPsec) connection security rules, Windows Service Hardening, and network protection from attacks that employ network fingerprinting. For more information about Windows Service Hardening, see http://go.microsoft.com/fwlink/?linkid=104976. Non-Microsoft firewall software that is compatible with Windows Vista and Windows Server 2008 can programmatically disable only the parts of Windows Firewall with Advanced Security that need to be disabled for compatibility. You should not disable the firewall yourself for this purpose. Stopping the service associated with Windows Firewall with Advanced Security is not supported by Microsoft.