Update: Using E2B v1.32 and later, you can boot from a partition image containing the Windows Install files. This means you can have lots of different .imgPTN files on your E2B hard disk and boot to any of the images in either MBR/BIOS CSM mode or UEFI mode without needing a Helper flash drive. It only takes a minute to create the image file from a Windows Install ISO and add it to your E2B drive.
Easy2Boot can install Windows Vista and later Windows OS's from any number of different Windows Install ISO files on the E2B USB drive, however if your E2B drive is a hard drive or fixed-disk type of Flash drive (i.e. not a removable Flash drive) then you also need to connect a USB 'removable' Flash drive (Helper drive) when you boot from the E2B Hard drive.
This is because the AutoUnattend.xml file is only detected by Windows PE Setup if it is on a removable drive (such as a removable USB Flash drive or DVD). The special E2B AutoUnattend.xml file (if detected by Windows PE) causes the whole Windows ISO to be loaded as a Virtual drive. If Windows Setup does not see a \Sources folder on any drive in the system, we get this message:
However, if you only ever want to install from just ONE Windows Install ISO from an E2B hard drive, you can just extract the \Sources folder from the ISO that you want to use and copy the whole \sources folder to the root of your E2B Hard drive. Then when Windows PE Setup boots, setup will see the \sources folder and be happy (i.e. you won't see the 'A required CD/DVD drive device driver is missing' message).
To get Windows 7 to prompt you to choose from a number of Windows 7 versions (Basic, Professional, Ultimate, etc.) then delete the \sources\ei.cfg file. So on your E2B USB HDD we have:
- \Sources\*.* (extracted contents of \sources folder from the Win7 Install ISO)
To save space, you can delete the large \sources\install.wim file inside the ISO file using a suitable ISO editing utility (e.g. Daemon Tools or Magic ISO).
P.S. To install Vista/7/8 from ISO files an E2B USB HDD (or if booting from a VM) without a USB removable Flash Helper drive, you can manually run \_ISO\e2b\Firadisk\LOADISO.cmd - see here for details.
[Edit] Win8.1 also needs just the \sources\install.wim and the \sources\setup.exe files.