RMPrepUSB is a user-friendly Windows graphical front-end which calls it's brother application RMPartUSB.
RMPartUSB is a Windows command line utility and does not have a GUI. RMPartUSB makes a partition of any size and is primarily intended for USB Flash Drive (UFD) memory sticks, although it can be used on USB hard drives or USB card readers to create a bootable partition.
RMPartUSB also places boot code on the USB device for either XP/WinPEv1 (ntldr), Vista/WinPEv2/Win7 (bootmgr), MS-DOS (io.sys) or FreeDos (kernel.sys). RMPartUSB does not place any files on the UFD - you must copy these over yourself or set the Copy OS Files option in RMPrepUSB to copy over the contents of a folder of your choice.