Network Traffic

Can anyone tell me if windows server 2003 has any built in utilities to monitor network trafic. I will start by stating that I am very new to server 2003 and networking in gerneral. I know the basics but that is about it. My company is on a T1 connection and we are constantly get bogged down by something as I am pulling speeds of only 1.1 mb right now. I have a download going and it has not reached over 25kbs. How can I track down the issue? Any help is welcome….

Thanks in advance.