The best codec package is K-lite codec pack. The package contains all codecs needed to view various movie files and including support for sub titles.
K-Lite Codec Pack is a collection of codecs and related tools. Codecs are required to encode and/or decode (play) audio and video. The K-Lite Codec Pack is designed as a user-friendly solution for playing all your movie files. With the K-Lite Codec Pack you should be able to play 99% of all the movies that you download from the internet.
There are 6 different versions of the codec package:
Basic is what 99% of all people need or want.