Note, the Windows GUI Disk Manager will NOT edit partitions on a USB drive.
You must use the admin command line diskpart.exe utility.
^
In Linux, DParted can do far more than you wanted it to do.
See also:
Making bootable USB drives
http://www.easy2boot.com Apparently
can boot to an ISO or VHD disk image from a file on the drive while the drive
remains readable as a normal USB drive.