It is easy to prove that your ISP blocks Gnutella. Well, at least as long as you know what's going on on your machine. There might be some "personal fyrewa11z" which actually block Gnutella because P2P is dangermouse!!1

Anyway, just do a manual test using "telnet" or a similar terminal tool. Even Windows has that, right? Connect to a known external (i.e., not on your machine or local network) Gnutella peer with telnet and type these lines *exactly* as they are. Use Copy & Paste because you won't be able to type them fast enough manually:

GNUTELLA CONNECT/0.6
X-Ultrapeer: False
User-Agent: Human/1.0beta

and then hit ENTER twice get an empty line and wait a moment. A Gnutella peer would respond with at least one line like this:

GNUTELLA/0.6 200 OK
[a lot of header lines]

or

GNUTELLA/0.6 503 Full

If the connection simply terminates, then your either not connected to a Gnutella peer at all or there could be some Gnutella filter. If that happens try again but this time use normal HTTP. Connect and type this:

HEAD / HTTP/1.0

and then hit ENTER twice to get an empty line. A Gnutella peer or
web server would send a reply like this:

HTTP/1.0 200 OK

or

HTTP/1.1 406 Not Acceptable

The numbers and the message will vary but you should see something starting with "HTTP/" as response. Try both 2-3 times. It is possible that peers are overloaded and simply drop your connection. This can happen but it won't happen all the time. So if you get a HTTP response from the peer but the Gnutella handshake always causes a terminated response, you can be pretty sure that there IS an Gnutella filter active, you cannot be certain on which side though. It could be the ISP of the remote. However, if you try this with a couple of IP address from completely different ranges, you can be fairly certain that it's your ISP.

Some ISPs seemingly do not block Gnutella inside their own network which indicates they are more worried about traffic (because internal traffic does not cost them anything).

To find fresh addresses of peers, you can simply open this URL with your browser:
http://galvatron.dyndns.org:59009/gw...1.0&hostfile=1

This works with all GWebCaches listed here:
http://gcachescan.jonatkins.com/

Just replace the part before the '?' with any of the listed URLs. Actually if you cannot load any of those URLs at all, you know that your ISP is dead serious about blocking Gnutella.

I know this may sound more complicated than it actually is. It would be easy to automice this check with fairly simply scripts but (un)fortunately, Windows is not really programmer friendly, so you have to find someone else to write such a check tool for Windows.