@warriorrider: Thanks for your help, but like cwhlam, it doesn't work for me (using MapSend DirectRoute 2.0).
I have a copy of 1.0 that I'll probably use; I read that the map updates from 1.0 to 2.0 were minor and I really need to get new detail maps on my eXplorist 500.
If anyone knows whether MapSend DirectRoute 3.0 works with Vista, please post here (with instructions, if applicable).
I've yet to try the eXplorist 600 driver on my 500, but I'll post back when I do (if I forget please PM me).
All the best.