Short journey for accelerated HD movie playback under Windows XP

I thought the subject is ridiculously simple. No, it is not. I have a Windows XP computer (Athlon X2 5200+, AMD 6450 HD) which is capable to decode 720p/1080p content by CPU, but I wanted to utilize the GPU now. I thought it works like out-of-box and I struggled for couple of hours, tried many players (including settings tweaking, googling, reading forums): BSPlayer, MKPlayer, VLC, MP Classic, WMP etc., but it just did not work. Then I installed the only player which succeeded from the beginning: PotPlayer. CPU usage dropped to 5 % instead of 60-85 %, nice.