Format Your External Hard Disk That Support Mac and Windows with Apple OSX
If you have an external hard disk or thumb drive and you would like to access(read/write) the hard disk on both Mac and Windows, you can format the hard disk with Disk Utility in Mac into several partitions like FAT32, UFS and Max OS Format.
Go to Finder, and Application > Utilities, and launch the program Disk Utility. Next, I will show you how to format a Thumb Drive into 2 Partitions. When Disk Utility is launched, you can see your Hard Disk/Thumb Drive is shown on the left Panel as the picture shown below;
Next, go to Partition tab to start partition your Drive, you can split the Drive into 2 partitions and on the Format menu, select one for MS-DOS (FAT) and another as Mac OS Extended. Depend on your own requirement, you can split it into 50% 50% or 70% 30%. After you have configured the setting, click on apply (If you are confirmed with the setting.). Your thumb drive will now partition and format.