What is binding this port?

Try netstat -anb

C:\> netstat -anb

Active Connections

  Proto  Local Address          Foreign Address        State           PID
  TCP    0.0.0.0:80             0.0.0.0:0              LISTENING       1724
  [Apache.exe]

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Update: That a in -anb is there for a reason!

C:\> netstat /?

Displays protocol statistics and current TCP/IP network connections.

NETSTAT [-a] [-b] [-e] [-n] [-o] [-p proto] [-r] [-s] [-v] [interval]

  -a            Displays all connections and listening ports.
                                         ^^^^^^^^^^^^^^^^^^^^
                                         ||||||||||||||||||||

For future reference, Sysinternals has a lot of great tools for discovering what is happening on your machine. tcpview, for example, gives you real-time monitoring of TCP/UDP sockets, filemon can show you activity related to file accesses ... the list goes on.