sorry for the delay in replying.
the operating system is windows xp. As for all the other applications i have installed, do you mean all the programs that come under the list of "all programs" in the start button? (i know, stupid question, but I wouldn't want to make a list of all the stuff in there if you mean something else!). As for "process explorer screenshot", i have no idea what that means.
By the way i uninstalled and re-installed itunes, nothing changed. I also removed the latest update to WMP and re-installed it, nothing changed either. For a few days now my Windows automatic update has been downloading stuff pretty much everyday, but it's probably unrelated as WMP and itunes are still blocked.
I'm trying to open other programs that i can use to play music, as it appears only the players are blocked, but RealPlayer is fine, so is Arcade (came with the computer, an Acer), and EmoDio (came with Samsung mp3 player) works also. So it seems only the 2 players above are being targeted. As far as I can tell, nothing else has been blocked by the firewall, but recently i have only been using my laptop for music and internet access, so there may be others that i haven't noticed are being blocked.