It’s a bit confusing what you want.
1 The drive is now formatted for Mac?
2 Do you want to use the drive on both Mac and Windows?
3 NTFS is for Windows and is read only on Mac Mac format is unusable on Windows unless you buy software
4 To reformat use Windows PC and this link should help http://wdc.custhelp.com/app/answers/detail/a_id/291/session/L2F2LzEvc25vLzEvdGltZS8xMzE3NzQ4NzQ0L3NpZC84bzUzMUtGaw%3D%3D
5 After formatting NTFS download NTFS-3G http://mac-free.com/download/NTFS-3G.html on Mac to use drive on Mac
Joe