If you already have Quicktime 7 installed (it came out late last week for PC) go here:
http://www.apple.com/quicktime/guide/hd/
Then go to the link up top and watch some of the HD samples.
If you don't - go install it here:
http://www.apple.com/quicktime/
If you try to watch the HD videos without the newest version of Quicktime.. you will only get the audio.. no picture.
This is the future of streaming video - if you want HD feeds for your site, contact me and I'll let you know what I have and will send you some demos.