If your E2B USB drive is not a 'Removable' type of USB Flash drive, then installing direcly from a Windows ISO file will not work.
You will typically see a 'Windows CD/DVD device driver required' message...
Installing Windows 7/8/10 from an E2B Hard Disk (instead of a Removable Flash drive).
USB Flash drives can be 'Removable' or 'Fixed Disk' type.
USB Hard drives are always of the 'Fixed Disk' type.
When Windows Setup runs (Vista and later versions), Setup will look for a file called \AutoUnattend.xml on a removable drive. E2B relies on this feature when using a Windows ISO file. The AutoUnattend.xml file generated by E2B contains an entry which causes Windows Setup to run a utility (FiraDisk and/or ImDisk - you will see a blue command shell box) which finds and then loads the Windows Install ISO file as a virtual DVD drive so that Windows Setup can access the files inside the ISO.
Note: Some modern ('Windows certified') USB flash drives can also appear as a hard disk to Windows. Run RMPrepUSB and select the USB flash drive - check that it is listed as a (Removable) drive (see screenshot above). If not, you will need to follow these instructions and use a secondary 'removable' Helper USB Flash drive.
Windows XP+WinPE (see section below), Vista and later OS installs will not work if you only use an Easy2Boot USB Hard Disk (you will get a 'Driver required' error message).
Note: Instead of using a Helper Flash drive, you can convert the Windows ISO into a .imgPTN file using MakePartImage. Then you do not need a Helper Flash drive and the install process will be the same as if you had just extracted the Windows Install ISO files to a bootable USB drive.
Another alternative is to use WinNTSetup to install Windows.
To make Windows Vista/7/8/2012/SVR2K8 installs work from an Easy2Boot USB Hard/Fixed Disk (Local Disk in Windows Explorer), you must use the Easy2Boot drive togetherwith a spare, writeable, 'removable' USB 'Helper' flash drive, as follows:
1. Prepare your Easy2Boot USB Hard/Fixed disk as described in this tutorial.
Add your Windows install ISOs to the \_ISO\Windows\xxx sub-folders and check that the menus work and can detect your Windows ISO files.
Run WinContig (RMPrepUSB - CTRL+F2) to make the files contiguous.
2. On any small spare USB Flash drive that you have available - this drive must be seen by Windows as a writeable, removable disk which is usually the case for small USB flash drives - check that RMPrepUSB reports it as (Removable):
Copy the 3 files - Unattend.xml, AutoUnattend.xml andWINHELPER.USB files from the \_ISO\docs\USB FLASH DRIVE HELPER FILES folder to the root of the USB helper Flash drive using Windows Explorer (e.g. U:\).
IMPORTANT: When you use the Easy2Boot USB Hard disk+flash drive combination, the only \WINHELPER.USB file in the whole system, on any disk volume or filesystem, should be the one on the USB 'Helper' Flash drive. Do not copy WINHELPER.USB to the root of your Easy2Boot USB hard disk or anywhere else! The USB 'Helper' Flash drive (or any other drive in the system) should not contain the Easy2Boot \_ISO\E2B folders, otherwise Easy2Boot may get confused (certain files are searched for during Windows installs and so the only Easy2Boot files should be on the boot device).
3. To install Windows Vista/7/8/etc. (or XP via WinPE method) onto a target system, connect both the Easy2Boot USB drive and the USB flash drive - but boot from the Easy2Boot drive.
This will only work when booting from a real system (it will not work under a Virtual Machine or Emulator). Even just using a single E2B USB removable flash drive will not work because a USB Flash drive is seen as a hard disk by VM's and so the AutoUnattend.xml on the flash drive is not found by Windows Setup.
WARNING: If you use a multiple-partition USB flash drive and the xml files are not on the first partition then Windows Vista/7/8 installs will not work because Windows Setup only mounts the first partition of a flash drive and so cannot see any of the files on the other partitions of the flash drive!
IMPORTANT: Only one drive in the entire system must contain the E2B files - do not put the E2B files and folders on the Helper USB drive!