CPU Usage while decoding HD with AMD X 2 4600 and Geforce 6150 LE

I was curious why my CPU usage is so high when decoding HD with my new Media Center PC (Purchased it from a friend who never used it for HD) When I read reviews of the 6150 LE, it indicated CPU Usage was only 20-30% even when decoding 1080/h264. I am getting readings in the 60-80% range. I am fine with getting a new card if that is what is needed for good peformance..I just am wondering why reviews of the 6150 LE indicated it had relatively low CPU usage but I am getting crappy numbers..

System is HP AMD X2 4600
2 GB Ram
Geforce 6150 LE
Windows Vista Home Premium..

Here's what I would do:

1) run msconfig and disable EVERYTHING save Windows and security programs.
2) Uninstall EVERYTHING you don't need or while ever use.
3) Run a registry cleaner once you do the first two steps.

Retail machines come with a lot of crapware that wants to start up all the time. Get rid of everything you don't need and see if that helps.