I think maybe there is an easy way to re-partition it under windows.

1. Put the SD to the external slot of the N8x0
2. Connect the supplied cable from the windows PC and the N8x0
3. Right click on "My Computer" choose "Manage"
4. Click "Disk Management" to find the SD
5. Pay attention to the SD label,size,.... then select it to re-partion, format, ...