The Windows Vista Product Guide is available up on ms.com. It seems to have finished its’ appearing-disappearing act and is up there permanently. Some links strangely point directly to the word doc forcing you to download a 60MB file instead of the smaller xps version. Here is the link to the page where you can make the choice between the two versions.
The doc is actually a great read about all the stuff in Windows Vista. A good chapter on XPS is in there.