As you've found, formatting an MP3 player is not always advisable.

Please supply the model number because Craig has a range of products.

Meantime if it's a simple stick model (like a memory stick) the chances are it's a SigmaTel design and those will tolerate formatting as Fat32 (so if your daughter selected NTFS you need to reformat it).
When finished disconnect (and insert a fresh battery) and the device may boot up and apply the necessary software and folders from firmware.

Failing that, with the stick models it may help to remove the battery and press the Menu or Play button as you connect to the PC. This should then activate Windows' Found New Hardware sequence.