I cant add tv shows/movies = system freezes

I cannot use QuickTime to open these formats, when I do, my entire system freezes and causes a hard drive failure. It's unberable. So instead I use VLC player to watch those video formats but recently I've purchased an iPod Touch and I want to put my tv episodes into it, meaning I need to use iTunes. When I add the file, my system freezes and causes the exact thing. Can someone please help?