Software Code Sticker on PC

The firm I work for is disposing of 100 PC’s, all which have W2K or XP Home license stickers on the boxes. All were reimaged with Enterprise XP Pro when new, and are being wiped clean. What is the legal status of reloading W2K or XP Home on the machines for future use? I know this brings up the grey area discussions, but what is the legal implications, does anyone really know?