Can you please tell me how to create a hybrid MBR/GPT partition on the USB drive? I need the MBR for the boot as my BIOS doesn't boot GPT partitions.
A standard BIOS doesn't really care about the partition table; the BIOS just reads the first sector of the hard disk and executes the code it finds there. That said, some implementations do more than this, and may refuse to boot from GPT disks. These are typically actually EFIs, which may use clues in the partition table to determine the boot mode. My Web page on the topic describes the problem, and workarounds, in more detail. Most commonly, setting the boot/active flag on the 0xEE partition in the MBR (using a GPT-unaware partitioning tool) often works around the problem.
If you're trying to boot Windows using the USB flash drive, be aware that it will see the MBR side of any disk that uses a hybrid MBR; thus, creating a hybrid MBR is pretty pointless -- you might as well just create a regular MBR disk and save yourself the hassles and risks of a hybrid MBR. For that matter, the advantages of GPT are modest except on disks larger than 2TiB, so even with other OSes, using a straight-up MBR on the disk might make more sense than using GPT. Alternatively, if the computer(s) on which you want to boot the disk use EFI, you might consider using an EFI boot loader.
All that said, if you insist on using a hybrid MBR, my GPT fdisk (
gdisk) can do the trick.