>If I want to do a demonstration of an application on from an XP computer to another XP computer I know that I can use NetMeeting.
>
>If I want to do a demonstration of an application on from a Vista computer to another Vista computer I know that I can use Meeting Space.
>
>What can I use if I want to do a demonstration from Vista to XP coming from the MS world?

http://www.LogMeIn.com - compare the features and price with others. One difference is that they don't advertise in broadcast media.

HTH,