Combined Community Codec Pack is a collection of codecs (including some belonging to other players) which isolates itself to ensure that it is not harmful or conflictive to the system.
Before installing anything, you can immediately check that the previous statement is correct as CCCP detects whether a conflicting component is included (from another pack for example) and will request permission to disable this.
This pack installs: Haali Media Splitter (MKV, MP4, OGM, AVI), VSFilter 2.37 (SSA/ASS, SRT, VOBSUB Subtitles), ffdshow 2005-12-20 CCCP build (H.264/AVC, DivX, XviD), WMV9VCM (Windows Media codecs), Media Player Classic 6.4.8.7 y Zoom Player Standard 4.51.