WMRoot is the Windows Media root directory. Windows Media Services creates this folder by default during setup. In it you will find sample content files, a sample playlist file, and a sample wrapper playlist that you can use to learn about Windows Media Services. The Default publishing point uses %systemdrive%\WMPub\WMRoot as its source. Once Windows Media Services is running on your server, you can use a player to connect and view the sample content by using the following URL: mms://server_name/content_clip1.wmv.
You can place any existing content you have into WMRoot and quickly start streaming content.