When you purchase a USB hard drive, the drive is formatted as one single partition. Splitting the drive into multiple partitions allows you to keep your data separate from other data. For example, one partition can be used for system backups, while the other can store the music and videos that won't fit on your internal hard drive. Splitting the USB drive into multiple partitions is simple. It is important to back up any data on the drive before splitting.
Connect the hard drive to the computer via USB cable.
Open the "Start" menu, right click "Computer," select "Manage." Select "Storage," then "Disk Management."
Right click the partition you wish to split on the USB drive, select "Shrink Volume."
Enter the amount of megabytes by which to shrink the drive. This is the amount of space that will be available to create the second partition. Click "Shrink." The partition will be shrunk, resulting in "Unallocated Space."
Right click the unallocated space, select "New Simple Volume."
Enter a name for the second partition, the desired size and file system format. Click "Next," then "Finish." The result will be two partitions on the USB hard drive.
Back up the data on the partition before splitting as the process may erase the contents of the drive. Once split, you can restore the data to the desired partitions.