it protects you from bad viruses and programs that make your computer do things without your permission..... the windows firewall should be left on always no matter what. unless you want a computer...
Firewall is needed in network because it blocks untrusted network and allow trusted network and it makes your network secure and easy to use....... ( VIKRAM SINGH )
It is perfectly acceptable to run both at the same time. I do at home, and have never had a problem myself. -- There is no problem in using both, but Windows Firewall is superflous when you have got...