When we last visited Wal-Mart’s attempt at DRM-free music, they had only managed to get EMI and Universal Music Group signed up for the DRM-free portion of their store. They’ve now decided to go all-MP3, but they’re still stuck without Warner Music Group and Sony BMG, which are unfortunately the top two record labels.As Wal-Mart switches to the MP3 music format and redesigns its music store, it leaves behind Microsoft’s digital rights management technology, which prevented the songs it sold from being played