Well I think I figured it out. HP has the VISTA driver locked down where I can only install the driver from their site and not the ATI site. Does that sound correct?
However I found a site which mods the ATI driver and allows you to install the most current driver from ATI as well as use the ATI control center application.
This had a positive and negative effect on my computer.
It has a positive effect because Windows Media Player recordings in standard definition in full screen they now play smooth and are no longer pixelated/ blocky and stuttering as they were with the WDDM driver. Previously if I played full screen in Sling Media, Windows Media Center, or Windows Media Player I had playback issues which were not present on same computer when running XP.
On the down side now when I playback Media Center DVR files recorded in HD I initially get sound and a full screen which is green in color but no video. But if I take Media Center out of Full Screen mode to window mode then the video appears. Then I put it back in full screen mode and the video works fine.
With the default HP/windows WDDM driver the HD playback was very bad due to severe stutter & blockiness. Now it runs smooth and normal. I just have to swap from full screen to window and back to full screen again to take care of the green screen issue.
So used the mod tool below along has allowed my PC to run video normally again due to the use of a current ATI driver.
Here is the location of the file which allows you to install the current ATI driver and use control center:http://www.driverheaven.net/modtool/