Remote Assistance, Routers, & Windows Messenger

Hi,

I have been trying to help a friend of mine with some computer problems. I
have XP Pro and he as XP Home. Both of us are behind routers and have
firewalls. We have spent much time trying to get connected, initially via
requests sent by email. I have searched the knowledge base and found out it
won't work with both of us having routers. It recommended using Windows
Messenger. We have tried this with no luck. Via Messenger, he can send a
request, I can accept the request, but he does not always receive the prompt
to accept my connection and when he does, my remote assistance window never
opens? I have poored over many KB articles and search many boards with no
success. I am beginning to wonder if what I am trying to do just can't be
done. Any help is appreciated.