In this day and age of Business 2.0, many organizations relay on VPN access for their users. You can offer them remote assistance. The process may be a bit more difficult. First off, you may have to use the clients IP address. You can ask the user for the IP address, but with Vista assigning both IPv4 and IPv6 addresses to each physical and virtual adapter, this could be frustrating for all parties. If you have access to the RRAS server the user is connected to, you can look up the properties of the connection. This should tell you the IP address to use in the offer. If DHCP Relay is enabled on the RRAS server, you may be able to look at your DHCP server for the IP address or use the name of the client.
Port issues on the local client, as well as the local network the client is on, will have an impact on your connection. I’ve found that DCOM port 135 seams to be the one most people are talking about. Here is the procedure to create an exception in the Windows Firewall for it (http://support.microsoft.com/kb/954386). Nothing can be done about a remote networks firewall settings. I found that Startbucks (Pay for use) and Panera Bread (Free Internet) allows me to remote access a VPN client.