On October 9, 2008, WalMart will be shutting down the DRM servers which support digital music tracks purchased from WalMart before February 2008, which is when they moved to DRM-free MP3 files.
Unless you burn your purchases to CD before that date, you will lose the ability to move those files to different PCs or devices, or burn them to CD, or backup and restore them; they will only be playable on the originally-authorized PC, and that authorization could be inadvertently revoked by other patches or programs without your prior knowledge or consent.
Burn those files to CD (as an audio CD, not a data CD!) or risk losing them.
I’m not posting this as a rant against DRM–though writing such a rant is certainly tempting–but in the hopes that no one in this community will be bitten and lose access to any of their music files.
–James