that's ok I suspect to do it in cmd might require fdisk on a boot cd with a dos driver for whatever sd hardware etc.

Incidentally a jukebox format might be low level since a 2GB card in the panasonic reader takes ~5 minutes. The sd formatter program linked earlier only takes a couple of seconds in the same reader so probably only replaces the allocation table, but nevertheless will delete 7k partitions. As far as the ability to accept audio is concerned the result is identical.