Sometimes I will start up a server process and get an error about a port already in use. This problem always bedeviled me before as I randomly stopped processes until that port was freed up.
But today a colleague pointed out a great Microsoft tool called TcpView.
TCPView is a Windows program that will show you detailed listings of all TCP and UDP endpoints on your system, including the local and remote addresses and state of TCP connections. On Windows Server 2008, Vista, NT, 2000 and XP TCPView also reports the name of the process that owns the endpoint. TCPView provides a more informative and conveniently presented subset of the Netstat program that ships with Windows. The TCPView download includes Tcpvcon, a command-line version with the same functionality.
With TCPView I discovered and stopped the anti-virus program which was taking up one of the ports that the server needed. This is much nicer than netstat. 🙂
Another nice tool to discover what programs are holding onto files is Process Explorer.
Update Feb 27 2014: Fortunately this still works on Windows 8.0 even though I am not sure if there has been any new development on it since 2011.