How to determine who occupied port 80 (windows xp)?

Question

local server

Suddenly, the local Apache stopped running.
The event log says
"The Apache service named reported the following error:
>>> (OS 10048)Only one usage of each socket address (protocol/network address/port) is normally permitted. : make_sock: could not bind to address 0.0 .0.0:80 ."
At the same time, netstat -o does not show anything that would hold on to the 80th port.
If you go to localhost:80 in a browser, you get a blank page.
Telnet to localhos:80 fails.
Suspicion falls on experiments with i2p and tor - but tor is inactive, i uninstalled i2p. How to find out what is the problem?

Answer 1

If skype is running, then it may have occupied port 80.

Answer 2

netstat

Answer 3

more precisely, netstat -a

Answer 4

netstat -a -o -b Show processes

Answer 5

Use this tool http://technet.microsoft.com/de-de/sysinternals/bb897437.aspx