Hello, I had installed K-Lite Codec Pack some weeks ago. After some while, I uninstalled it and instead installed Windows 7 Codecs. I then tried to play a 1080p m2ts file in Windows Media Center and it lagged horribly. I went to the Windows 7 Codecs forum to get help and the author told me that Windows 7 natively supported m2ts playback and I had to do a complete reinstall of the OS to get it back. The file plays perfectly well on Windows XP, on my other partition in the hard drive.