How to use an existing USB Hard drive



You may have a large USB HDD which has many files on it which you do not wish to delete.
However, due to BIOS incompatibilities in many systems, the maximum size of partition that you should have for a bootable USB drive is 128GB.
If you have just one large HDD with a single partition of over 128GB, you should split it into two partitions
  • Partition 1: 128GiB (or smaller) Primary NTFS (for E2B)
  • Partition 2: (remaining space)   Primary NTFS (your files)
If possible, move the start of the first partition to leave 128Gb free and then create a new first partition of 128GB.
If this cannot be done by using a disk partitioning tool such as EaseUS Partition Master Free Edition, then first shrink the single partition to 128GB and then create a new 2nd partition. You can then move your files to the second partition to leave space for the E2B files and bootable ISOs.
Note that this kind of partition moving and re-sizing carries a risk of losing data and it does not always work without data loss!
E2B also requires unused free space on the first partition so that files can be easily and quickly defragmented.
Note: The process of shrinking partitions and moving files can be very slow on USB drives and also unsafe. I highly recommend that you transfer your files from the USB drive to a different drive and then use the E2B_Maker.exe GUI tool to re-partition and re-format your USB drive. This will make a 128GiB partition + a small 31K partition. You can then delete the small 2nd partition and make a large 2nd Primary NTFS partition on the USB drive and copy your own files to the 2nd partition.


Once you have a multiple-partition USB HDD, you can install E2B onto the first partition.
1. Run the E2B .exe download and choose the Update E2B drive button.
2. Select the first partition of the USB drive by entering it's drive letter
3. Ignore the warning that it is not an E2B drive, it will then copy the E2B files to the selected partition
4. When the file copy has finished, you need to install grub4dos to make the USB drive bootable.
Note: If the drive was previously used as a bootable drive, then installing grub4dos will, of course, now make it boot to E2B instead.
Run RMPrepUSB (press Ctrl+Z if you have a large USB HDD) and make sure your USB HDD is selected. Now proceed with these 2 actions:
  • Install grub4dos - MBR=Yes  (do NOT copy the grldr file)
  • Install grub4dos - MBR=No   (do NOT copy the grldr file)
5. Check that the USB HDD will now boot to E2B by using RMPrepUSB - F11   or double-click on the USB drive \QEMU_MENU_TEST (run as admin).cmd file.
You should see the E2B menu - press F10 to quit E2B.
Tip: Download the Add_bootmgr_to_E2B executable to automatically add the correct version of bootmgr to your E2B drive. This is required if you wish to boot .VHD and .WIM files.


  • You must use the first partition of the USB drive for E2B files and payloads (ISOs)
  • The first partition should be < 128GB (some BIOSes cannot access files beyond 128GB on USB drives)
  • The USB HDD should contain 2 partitions. If it only contains one partition, create a 2nd Primary partition (of any size - even if very small) for BIOS compatibility.
  • You USB HDD should not contain more than 2 Primary partitions. When in use, E2B will create and delete partition #3 and partition #4.
  • E2B will not boot to the Main Menu unless partition #4 is unused. WARNING: E2B will prompt you to delete partition #4, if it exists.
  • Unless you have a specific requirement, use NTFS for the E2B partition. You can UEFI-boot from an NTFS E2B partition using .imgPTN image files.
  • You can place your personal files on the E2B partition as well, if you wish - it will just use up space. Do not place your own (non-E2B related) files under the \_ISO folder or else they will be defragmented by the E2B utility. Use your own folder, e.g. \Steve.