Shortly after the first day of presentations at PDC2008, Microsoft posted a (.wmv format) Windows 7 preview video to the Microsoft Download Center.
The Windows 7 video features Microsoft's Mike Nash, CVP Product Manager, Windows.
The 106MB file can be downloaded here.
Related: The new Microsoft Azure cloud computing website can now be found here.
Update Oct 28 PM: Microsoft's PDC2008 Virtual Pressroom now has numerous online (downloadable) videos, and we are sharing others' coverage, as always, in the 'shared feed' (at right).