Changing the Partition Map Scheme for a disk using a Mac

There's a number of reasons why you might want to change the Partition Map Scheme of a disk but the most likely is that you're setting up the disk so that you boot a particular OS from it.

On the mac the default application supplied for changing this is Disk Utility. You can find this in the Utilities directory in the Applications directory.

You can use Disk Utility to both see what type of Partition Map Scheme is being used and to change it.

Checking the Partition Map Scheme

1.  Go the USB disk in Disk Utility
   
2. At bottom right you can see the Partition Map Scheme that is currently being used, in this case it's Master Boot Record.

Changing the Partition Map Scheme

Following these instructions will result in all data on the disk being lost so be careful

1.  Go the USB disk in Disk Utility and select the partition tab
2.  In the Volume Scheme select the number of partitions that you want (if in doubt use 1 Partition)
3. Select the format (use MS-DOS (FAT) if you want to use the disk on other platforms)
   
   
   
4. Click the Options... button at the bottom and select the Partition Map Scheme you want to use
   
   
   
5. Click Apply to write the partition: this will erase any data on the disk