Is the USB drive a Removable-type flash drive?
If so, WIndows will not be able to see the AutoUnattend,xml file because Windows cannot see the 2nd partition.
Also, even if it could see the XML file, it will not be able to see the ISO and load it using ImDisk because that is also on the 2nd partition.
There is a sample mnu file which will swap round the two partitions. Then the Win7 install will work. But you will need to swap it back again afterwards.
Note that some systems will refuse the MBR boot from a USB disk that has FAT32+UEFI files (even with CSM mode enabled).
So your USB drive can never MBR boot to WinPE or E2B on these systems.