You should use the remote assistance feature to do this instead of remote
desktop it works great. To get to remote assistance goto help and support
then under ask a friend for help you will find Invite a Friend to help with
remote assistance. Note this must be done on the remote or person who needs
help computer and you must have e-mail on both computers because what the
system does is send an email with a link which will connect you to the remote
computer automatically. I don't know if you have to do anything different
with a router (ie forwarding ports ect) than what you do with remote desktop
so this could be an issue.
Hope this helps
Parker