Where does the tag information come from?

When you put a CD in your drive to be played or ripped for the first time, Media Center gets the track information from the CD itself if it has "CD-Text". If there is no such information, it checks the cdplayer.ini file in the Windows directory. If it still can't get the information, and "on-line CD lookup" is enabled (Tools > Options > CD) it searches the YADB on-line database (see http://www.yadb.com/) for a match (you must be connected to the Internet). If it can't find it on-line, it asks if you if you want to fill in the info and submit it to YADB. If you don't fill in the information, the tracks will be named "track 1, track 2", etc.

Once it has info for an audio CD, it is stored in the database so the next time you insert this CD it just grabs all the information instantly from it's own database without any YADB or cdplayer.ini checking.