Note: You can make a 'partition image' file of any Vista/7/8/10 Windows Installer ISO using MakePartImage - then you won't need to use a 'Helper' Flash drive. See here for more details.
Tip: A WinHelper USB drive is not usually required for E2B v1.A8 or later versions unless you have less than 1.5GB RAM in the system.

- 'A required CD/DVD drive device driver is missing.' Windows Setup pop-up message (see above) or 'ERROR - COULD NOT FIND E2B DRIVE! Press any key to continue . . .'
- A 'LOADISO' blue console DOS window is NOT seen (see below for example blue console windows).
- Not enough memory to use WIMBOOT (need 1.5GB+) and you are using a USB Hard Disk or USB FIxed-Disk type flash drive/SSD (not a Removable Flash drive)
- WinPE does not contain a suitable USB 2 or USB 3 driver for that particular system (e.g. old Win7 used on new systems)
- You have copied the contents of an E2B Removable USB drive to a USB Hard drive or Fixed-disk type of USB drive
- Your ISO is incompatible with WIMBOOT (WIMBOOT was added into E2B v1.A8 and later versions)
- Use E2B v1.A8 or later and a system with 2GB or more of RAM
- Connect a small 'WinHelper' USB Flash drive as well as the E2B hard drive - OR - convert the Windows ISO to a .imgPTN file
- For Windows 7 you may need to add USB 3 drivers into the Windows ISO - you can add Intel and AMD USB 3.0 drivers into a Win7 ISO using this tool. Try unplugging the E2B USB drive and connecing it to a different USB 2 port.
- If using a 'fixed-disk' type of E2B USB drive, ensure the 'set NOHELPER=1' line is NOT present in the \_ISO\MyE2B.cfg file.
- To prevent WIMBOOT from being used, press ENTER key when prompted (v1.A9+) - or add the characters 'NOWIMBOOT' into the filename - e.g. Windows 10 x64 (noWimboot).iso (v1.B1+).

See YouTube video here.
If you have an E2B USB Hard disk or you have an E2B USB Flash drive of the 'Fixed Disk'/'Local Disk' type (as shown by RMPrepUSB or Windows Explorer), then some WinPE .ISOs and all Vista, Win7, SVR2K8, SVR2012 and Win8 Windows Install ISOs and WinPE ISOs may not work correctly because you will not get the blue console window which runs ImDisk and loads the ISO as a virtual DVD.
E2B USB HDD + 'WinHelper' Flash drive
It may be helpful to you, if you understand how E2B works and why E2B needs to have a Removable USB drive to get Windows Install ISOs to work - see here and look for the 'Windows Install ISOs' section, for the details. If E2B uses the WIMBOOT process, a Removable USB drive is not required.
Zalman or IODDIf you have an IODD 2531 or 2541, unzip \_ISO\docs\USB FLASH DRIVE HELPER FILES\E2B_WinHelper_&DW.zip and simply load the \_ISO\docs\USB FLASH DRIVE HELPER FILES\E2B_WinHelper_&DW.RMD file as a virtual drive using the jog wheel. This will then emulate a Removable WinHelper Flash drive.Tip: The E2B_WinHelper_&DW.RMD file can be copied to the \_ISO folder and loaded using the jog wheel.
How to make a 'WinHelper' USB Flash Drive for Windows .ISO payload files
To fix the 'device driver is missing' issue, you need to make an extra USB Flash 'Helper' drive as follows.

\_ISO\docs\USB FLASH DRIVE HELPER FILES
to the root of the USB Helper drive.
Ensure that you copy the files to the first partition of the Removable USB Flash drive (usually there is only one partition accessible in Windows anyway).
The files \WINHELPER.USB, \Autounattend.xml and \unattend.xml should now be present in the root of the WinHelper Flash drive.
Do NOT edit these files. They will be changed by E2B.
Note: If you convert the Windows ISO to a .imgPTN file, then you don't need to use a Helper Flash drive.
Troubleshooting Installing Windows using an E2B USB Helper flash drive
1. Ensure that the USB Helper flash drive is of the 'Removable' type (ensure it appears as a Removable Disk in Windows Explorer and in RMPrepUSB - see screenshot above)2. Check that it is detected by your BIOS - you should be able to see it listed by the BIOS boot selection menu - if not try using different USB ports and try formatting it using RMPrepUSB as FAT32+Boot as HDD options. If possible, always use the BIOS Boot Selection (BBS) menu (e.g. press F10 or F12) rather than set the boot order in the BIOS Boot-order menu.
3. You must install using a real system - running under a VM or Emulator will not work because the USB Flash drive will be detected as a 'Fixed Disk'.
4. Use a mainboard USB port that the BIOS can detect - if you have an add-in USB 3.0 PCI card, don't connect any USB drives to those ports.
5. If you are using a USB 3.0 port that is detected by the BIOS, then Vista and Win7 Installs won't work because those OS's don't contain USB 3.0 drivers - use USB 2.0 ports only for pre-Win8 OS's. Some USB 2.0 ports in modern systems are not recognised by Vista/Win7. In this case you will need to add USB 2.0 or 3.0 drivers into the ISO. Tip: If you have a USB 3 E2B drive and only USB 3 ports on the target system, sometimes it will work if you connect the E2B drive using a USB 2 extension cable to the USB 3 port - this will require a USB 2 driver to be used instead of a USB 3 driver.
6. Check that E2B has detected the Helper Flash drive - you should see an E2B progress message just before the Main menu is displayed 'Wiping /AutoUnattend.xml and /Unattend.xml files on WINHELPER.USB...'. Also the Helper drive LED should flash for about a second at this point. You should also see the Helper LED flash just before E2B boots from the Windows Install ISO file after the 'booting...' message.
7. If the Windows blue 'LOAD WINDOWS ISO USING IMDISK' console window did not appear before you get to the first Windows Install Setup screen (e.g. choose Country, etc.), press SHIFT+F10 to open a Windows console. Type NotePad and then open the \AutoUnattend.xml file on the Helper Flash drive with NotePad - it should contain lots of xml text. If not, it was not updated by E2B (probably because it was not detected by the BIOS)

This 'blue console window' loads the ISO file as a virtual DVD - it MUST run so that Setup will 'see' a DVD drive.
Manual method without needing a Helper Flash drive
2. As soon as Setup loads and asks you for a language/country, press the key combination SHIFT+F10 - a black console window should open (if SHIFT+F10 does not work, answer the next question and try SHIFT+F10 again)

Make the Helper drive bootable (not recommended)
You can also make the Helper Flash drive bootable, so that you can boot from either the E2B Hard disk or the E2B Helper flash drive, as follows:clearpause --wait=3 Booting from Easy2Boot USB Helper Flash Drive...find --set-root /_ISO/e2b/grub/menu.lstchainloader /grldrboot
Using a IODD DVD-emulation hard disk caddy