Apologies if this new is old hat but thought I would share it... Finished a partial build of my 1st HTPC (still need to add a tuner and BluRay). Used the a AMD 4850e and a Gigabyte GA-MA78GPM-DS2H 780G chipset motherboard as I had read great things about the 780g built in Hardware decoder for playing HD content. However, I was initially very dissappointed when KMPlayer, Media Player Classic HC and Media Portal built in player were all reporting 50-60% CPU. After loads of Googling I discovered the following on another site: It involves downloading the mpcvideodec.ax codec from the MPC-HC website and registering the file and then using the MPC Video Decoder filter for playing your H.264 files. Stand alone filters for MediaPortal - MediaPortal Forum The above has some details or you can download the file from the following location: SourceForge.net: Files Click on the standalone filters link for 32 or 62 bit and then get the MPCVideoDec.zip file. You then extract and copy the MPCVideoDec.ax file into your windows\system32 or similar and then do a regsrv32 on the file from a cmd prompt - in Vista make sure you run the cmd prompt as Admin even if your user is an Administrator - otherwise the registration will fail. Then in your Media Portal or Media Player Classic HC select the 'MPC Video Decoder' as the filter to use for H.264 files. I cannot get it to work for KMPlayer despite trying similar steps and reading an article (cannot enable the DVXA) - so have given up - Media Portal built in player seems fine as does the Media Player Classic. Have played a few 1080p MKV H.264 files for a few minutes each and for both the CPU usage seems to fluctuate between 2% and 10% - giving a rough average of 5%ish.