DMA open or closed for better media?

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http://www.linuxquestions.org – recently my windows XP pro crashed and so i reformatted wth fedora. when on windows i had some movies that played fine, like .aac or .mkv with no lag or bad pic. so now on fedora, with the same hardware ill use VLC or K media and its terrible. voices are off, grainy, stops a lot. i installed easylife to get the necessary plugins but still looks like garbage. so i was told to try and open my DMA to get a better experience. is this accurate? and how? 1 hard drive or all??? (HowTos)