Let me ask you simple thing, How many times it happens that you are just checking your mails and still find that your internet connection is working so slow.
Actually there are many apps which runs in the background and uses your internet connection and makes your connection slow and uses your bandwidth.
TCPEye is a free and useful app.It is network monitoring software that displays the list of all currently opened TCP/IP and UDP ports on your local computer.
For each port in the list, information about the process that opened the port is also displayed, including the process name, full path of the process, version information of the process (product name, file description, and so on), the time that the process was created, and the user that created it. In addition, TCPEye allows you to close unwanted TCP connections, kill the process that opened the ports, and save the TCP/UDP ports information to HTML file , XML file, or to tab-delimited text file. TCPEye also automatically mark with pink color suspicious TCP/UDP ports owned by unidentified applications
It works fine on Windows 95/98/Me/2000/XP/2003/Vista/Server 2008/7/NT