I am interested in buying my first MP3 player but I'm not sure how to know what different file types will play on what type of MP3 player. I imagine all players will play music that I download directly off of my store-bought CDs...is this correct? I have also noticed that Walmart's music-dowload website says that "the Apple iPod will not play Wal-Mart Music Downloads files. Our files are in the WMA format with Digital Rights Management (DRM) encryption. Many other media players will play our files." Is this also a problem with files from other music download sites? Will iPods not play any WMA files? What files can an iPod play and not play? Is there anything I need to know about other MP3 players when it comes to file compatability? Please help me know what to look out for on this issue, and remember I'm a newbie to MP3 players and am not completely familiar with all the different file types.