Windows media player, avast just uninstall it and try downloading an earlier version and updateing it if that version doesnt work, had a few anti virus refuse to install, uninstalling then downloading them again has always worked for me, if its possible i would conect hard drive to another computer and scan it, always a bit sus when anti virus doesnt install added to the problems your haveing with media player malware is definite possibility.

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Q6600-P5K Premium+Alphacool w/blocks
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