Sometimes it is easier to try and fix something over the phone rather than drive out to the clients house. The problem may be a quick fix, or the travelling may be too much to justify the time and gas. I've been looking for an easy to use, free method of providing remote desktop support. Currently I am checking out the SharedView Beta 2 from Microsoft.
The install requires administrative permissions. Close Messenger and any Office apps before installing.
The environment I tested in is not NAT. But I do have a admin configured firewall on this system and I did not have to make any exceptions.
Sharing can be by open application, or the entire destop.
It is worth checking out. It does require Windows Live ID /Passport account.