Hi
I prepared a USB Rescue drive from a Win 7 64-bit system.
The USB volume size made by Avast was 113MB.
The \boot\bcd was set to boot from \sources\boot.wim

Entry #1
Name: Windows Setup
BCD ID: {default}
Device: [boot]\sources\boot.wim
Bootloader Path: \windows\system32\boot\winload.exe

Problem is there is no \sources folder on the USB drive and no boot.wim!!!

So, of course, it does not boot. I am using todays free version.
HTH
Steve