Port 80 is being listened by SYSTEM (PID 4) on Windows

This is a famous problem.

And, a Microsoft engineer Raymond Chen answered here.

How can I determine why the System process is listening on port 80? | The Old New Thing

Here is the result of netstat -abo:

(...)
  Proto  Local Address          Foreign Address        State           PID
  TCP    0.0.0.0:80             myhostname:0          LISTENING       4
 Can not obtain ownership information
(...)
  TCP    [::]:80                myhostname:0          LISTENING       4
 Can not obtain ownership information
(...)

Use netstat -ao | findstr :80 for concise result.

HTTP.sys implements HTTP Server API to listen the ports. There are two ways to work around the issue.

Disable all services which are using HTTP.sys

Get the status of which services are using HTTP Server API by invoking netsh http show servicestate. In the following example, pid 2668 is registering HTTP://+:80/116B50EB-ECE2-41AC-8429-9F9E963361B7/.

Snapshot of HTTP service state (Server Session View):
-----------------------------------------------------

Server session ID: FF00000320000001
    Version: 2.0
    State: Active
    Properties:
        Max bandwidth: 4294967295
        Timeouts:
            Entity body timeout (secs): 120
            Drain entity body timeout (secs): 120
            Request queue timeout (secs): 120
            Idle connection timeout (secs): 120
            Header wait timeout (secs): 120
            Minimum send rate (bytes/sec): 150
    URL groups:
    URL group ID: FE00000340000001
        State: Active
        Request queue name: Request queue is unnamed.
        Properties:
            Max bandwidth: inherited
            Max connections: inherited
            Timeouts:
                Entity body timeout (secs): 120
                Drain entity body timeout (secs): 0
                Request queue timeout (secs): 0
                Idle connection timeout (secs): 0
                Header wait timeout (secs): 0
                Minimum send rate (bytes/sec): 0
            Authentication Configuration:
                Authentication schemes enabled:
                    Negotiate
            Number of registered URLs: 1
            Registered URLs:
                HTTP://+:80/116B50EB-ECE2-41AC-8429-9F9E963361B7/

Request queues:
    Request queue name: Request queue is unnamed.
        Version: 2.0
        State: Active
        Request queue 503 verbosity level: Basic
        Max requests: 1000
        Number of active processes attached: 1
        Process IDs:
            2668

Here is the excerpt of netsh http show urlacl.

    Reserved URL            : http://+:80/116B50EB-ECE2-41ac-8429-9F9E963361B7/
        User: NT AUTHORITY\NETWORK SERVICE
            Listen: Yes
            Delegate: No
            SDDL: D:(A;;GX;;;NS)

Then, google the keywords and disable all services.

Change listening addresses of HTTP.sys

By default, HTTP.sys listens 0.0.0.0 and [::], which means all IPv4 and IPv6 addresses. For example, by invoking netsh http add iplisten 127.0.0.2, you can change it to only IPv4 127.0.0.2. netsh http show iplisten reports the current status. You can restore the default setting by netsh http delete iplisten 127.0.0.2.