Here is a quote from the user manuel hope it helps
Media Library scans and consolidates the media contents of a USB drive into a
database through which you can easily locate media files. This feature is on by
The following conditions will prevent the Media Library from processing your media.
The USB device has read-only protection.
There is not enough hard drive space on the USB device. Your media center
needs some space to cache information, so that searches and scans are faster.
A note about metadata
Metadata is information about the data in a file that describes how, when, and by
whom a particular set of data (video, music, photographic, or any other type of data)
was collected, and how the data is formatted.
Not all files have metadata loaded. To add and edit metadata so that Media Library
can aggregate the files properly, you can use one of several tools including:
Adobe® Bridge (part of the Adobe Creative Suite)
abcAVI Tag Editor (freeware)
XnView 1.93.2 (freeware)
Windows media center