ok you should know first that you already loose your all contact details.
thats why my recomendation is to keep a back up. like I do.
ok let do it; firstly go to this page and download the HP USB Disk Storage Format Tool http://www.pcworld.com/downloads/file/f ... views.html
after the installation you should format your MJ device as "NTFS " complete format.
then you should be able to use it. maybe need to unplug and plug it back.
I hope to be helpful