I currently have a 640GB external HD that has 1 partition formatted as HSF+ Now I want to split some of the free space into a new FAT32 partition, without having to reformat the whole HD and losing all my data. I read that I'm supposed to be able to add new partitions in the Hard Disc Utility by clicking the "+" sign, without any loss of data. But in my case the "+" is not clickable and it says that this partition cannot be altered.

Can anyone tell me how to proceed. Or is it impossible without reformatting the whole disc?

I'm running OS X Snow Leopard 10.6.6


So far I know is that if you don't use the MAC OS EXTENDED Format and a GUID Partition table for the first partition you won't be able to adjust the size of the partition or squeeze in a new one. The only thing you can do is create a new partition with the free unpartitioned space on the ext. HD which is left over (supposed you left over some free unpartioned space).

  • Unfortunately I don't have unpartioned space left, and I don't have space to backup my data and reformat the whole disc :'( But thanks for the answer – Bart Mar 11 '11 at 20:48

You should unmount the disk before you try to change the partitions.

That should work.

  • Unmount is the same as right-clicking and ejecting the disc right? Unfortunately that's not working, it still says that this partition cannot be modified – Bart Mar 11 '11 at 17:26

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .