In XP, I just resolved my problem with the iTunes Remote. Try going to "Windows Firewall With Advanced Security." Just type that into the XP or 7 search in the Start Menu.
Once there, double click "Inbound Rules" on the left, and double click "Bonjour" (I have two rules for Bonjour, not sure if this is normal)
In the General tab, make sure that "Allow the connections" is checked. The problem I was having was in the "Advanced" tab. For "Profiles" make sure that "All Profiles" is used. Mine was on just Public profiles, which made it so that when I was connected to my home network (a private network), it would not work. There are other settings in these exceptions that might do the trick if this didn't work.
Help this helped.