Today I made a WinFE ISO based on a Win7PESE WinBuilder Project. To make the ISO, I followed the instructions on the Hacking Exposed website here.
Because I wanted to add lots of WinBuilder Win7SEPE ISOs to my E2B USB drive, I added the ISO file to my Easy2Boot NTFS Flash drive using this .mnu file.
title WinFE \n Note: Mount the E2B boot drive to use all applications
/%grub%/qrun.g4b force.iso01 /Win7PE_x86.iso
The WinBuilder ISO file must NOT be renamed and must be copied the root of the E2B drive so that the MountPEmedia.exe utility will find it and mount it as drive Y:. The name and path of the ISO file is pre-defined in the \Windows\System32\MountPEmedia.ini. This is written by WinBuilder when the ISO is created (the .ini file is inside the \sources\boot.wim file image).
It is important to ensure there is no \Win7PESE.ini file or \CdUSB.y file (which you may have extracted from a WinBuilder ISO previously) in the root of any drive as this could 'confuse' the MountPEmedia utility.
When the WinFE Write Protect Tool automatically launches after WinFE boots, you need to select the E2B USB drive and click the Mount button, otherwise the Y: drive (the mounted ISO file) will be inaccessible and you won't be able to run many of the utilities from the Desktop.
Other ways of adding WinBuilder PE ISOs and other PE ISOs to E2B can be found in the E2B Tutorial here.