Multiple partitions on a 'Removable' USB Flash drive
If you have a 'Removable' USB Flash drive, then Windows XP\7\8 will only access to the first Primary partition on the drive.
You can allow Windows to access the second partition by switching partition 1 with partition 2. To do this, you will need a utility which swaps the first table entry in the MBR partition table with the second table entry, you can use:
RMPrepUSB.exe - CTRL+O - 2
\_ISO\SWITCH_E2B.exe - Access Partition 2 on a Removable Drive
BootIce.exe - Select your Removable drive - Parts manage - Select 2nd partition - Set Accessible
Remember to switch the two partitions back again!
Exception: Windows 10 Creator update and later versions of Window 10 will mount and access a 2nd partition.