I use XP SP2. When I download the Vista Upgrade Advisor and click to open it I get a message saying that a problem has been encounterd and it will close. Any unsaved work will be lost. Can I get around this to find out if it is possible for me to do a download upgrade?

Try downloading the Advisor again and if it still doesn't work, you could try CNETs online upgrade advisor here. It tells you exactly the same things.