[Serusers] dead SIP service providers

Hello All, The following two sites appear to be SIP service providers: www.freeworlddialup.com/ voip.brujula.net/english/messenger-howto.html But when I follow their instruction for setting up Windiows Messenger 4.6, my login attempts tell me, "The service provider is temporarly unavailable, try again later" This makes me suspect that they have shut down their voip servers, and simply failed to delete their web pages. Does anybody know the status of these two companies? They have not responded to my email queries. Freeworlddialup provides a simple tool to evaluate your internet connection before trying their service. The tool consistently claims that my port 5060 is blocked, even though I am directly connected to my cable modem and have all firewalls turned off. It seems like this false result could be caused by an attempt establish a 5060 connection to a non-existant voip server, again supporting my theory that their server has been shut down. Does this theory make sense? Also, both providers say that they work with Windows Messenger 4.6 and 4.7 but not with 5.1. Did Microsoft commit some crime in version 5.1 to make it incompatible with third party SIP service providers? thanks for your help, Michael