The Media Player that comes with windows only supports the basic files. If all you need is to listen to some mp3 music files or watch DVDs, then it should be fine. What happens if a client send over some video that they just took or you received a training video from an instructor and you can't open them?
A few days ago I got a DVD from a real estate coach. I tried watching the movie but it does not play. The file have a .mp4 extension which the Windows Media Player on my Window Vista computer does not recognize. If I downloaded the Apple Quicktime, that might have worked. But I didn't want to constantly download a program for each file type that I wanted to play later. Instead I opted to download a Codec Pack that would support hundreds of different types of file types.
The Codec Pack is free and here are the instructions on getting it set up.
1. Go to http://www.free-codecs.com
2. At the left hand bar, there is a category called "Codec Packs"
3. Choose either the K-Lite Codec Pack or the K-Lite Mega Codec Pack, as they both will do the job.
4. Click the big "Download the K-Lite Mega Codec Pack."
5. The website will give you access to a page with a lot of download links spread across multiple mirrors. Whichever server you download from, the files will be the same.
6. Once the download is finished, run the .exe file by double clicking on it.
7. For non-experts, it is highly recommended to just install the recommended setup by clicking "Next."