Actually only having the K-Lite codec pack isn't enough. I strongly recommen you install all the codecs you can seperatly, downloaded from their respective sites. K-Lite codec pack will make MOST files play fine but ive had problems with it. Especially with the 3ivX codec, it just wouldn't play properly with K-Lite Codec Pack. Since then i isntalled all the codecs i found seperatly and the ones i didnt with the Codec Pack and everything is fine