Here's a good way to measure the video acceleration performance of your video card:
A Vista DreamScene oicean background encoded at full 1080p HD wmv in high bit rate:
http://lee.hdgreetings.com/2008/06/dreamscene
What's your CPU utilization when running this?
This is pure 1080p with zero noise, I rendered it in 30 hours using Maya 3d on a fast QC cpu.
I was surprised when someone told me it maxed out the CPU of their AMD 6000 system!
With a decent card I don't think CPU should nearly be maxed.
regards,
ltg