See people, this is why crap like DRM is important. Read this whole story over at TechCrunch but the upshot is that if you bought music from Wal-Mart with its DRM built-in, then you better get to your local Best Buy and pick up a stack of CD-Rs. Wal-mart is going DRM-free - good, right? - except that when it does, it will turn off those DRM servers and you won't be able to access your DRM-protected music files THAT YOU ALREADY PAID FOR!
Nice job huh? See, you didn't actually buy the songs - you bought a revocable license to those songs.
"Beginning October 9, we will no longer be able to assist with digital rights management issues for protected WMA files purchased from Walmart.com. If you do not back up your files before this date, you will no longer be able to transfer your songs to other computers or access your songs after changing or reinstalling your operating system or in the event of a system crash. Your music and video collections will still play on the originally authorized computer."