Using partitioning you can trick your computer into thinking it is connected to more than one drive, although there's only one. Luckily, you don't need two separate drives. In the Format menu for the partition that will be used for backups. Make sure 'Mac OS Extended (Journaled)' is selected If you want to partition the disk, click the Partition tab and Manually preparing a new disk for Time Machine Your preferred setup is not possible: OS X can't share an NTFS disk with Windows for backup because Time Machine needs HFS+ (from ):