The K-lite codec pack is a small installation file that will allow you to play just about any video or music extension on your computer's video player (Think of those .MKV and .FLAC files). To those who download a lot of subbed anime, this is very useful!
K-lite is great in that it exterminates the need of downloading extra video player software that have the codecs installed with them (besides the Windows 7 Video player is so nice you might not want to use anything else). As a final note, there are different types of codec packs they offer depending on your needs, though, I recommend the standard.
To those interested in downloading the link is right here.
>>>>As a side note, if you are one of those installers who simply press yes/next through all the options without giving a passing glance, I would consider taking your time through un-checking options such as installing the classic media player and not showing certain icons on your system tray.