UltraVNC has a great tool
UltraVNC Single Click - the person who needs help just runs one very small program and it connects to your computer and you get a remote desktop to their computer. You just need to email it to them or get them to download form a website..
NO software to install, NO configuration of their router/modem/thingy.
So far it has worked for me from NZ to Wales and you get treated to lots of oohs and aahhs as the mother-in-law watches the mouse move around the screen on its own...
If anyone wants any info ask me. You can get one that connects back to me from
here (if I am listening)