How about giving more information, like the video card you are working with, drivers installed, other software for that card, and the media player you are using.
You need DXVA capable video card, and software to enable it.
When you have everything in order;
In Windows Media player options (Tools>Options), in the performance tab, check the box which says enable DXVA for WMA files. When enabled, you will notice your CPU usage significantly decrease.
I want to ask if my hardware support DXVA, and where can I find a list.
Intel Celeron D 331, 2666 MHz
Intel(R) G41 Express Chipset
Intel(R) GMA 4500