Solution

There is no way to multicast-deliver these addon images to Windows 7 Machines "Partition 2" without having to edit each one and change the partition number inside the ZMG file.

Customer used the following to fix:

Remove 100Mb System Reserved Windows 7 Boot partition:
• log in with administrator privileges.
• Open disk management (diskmgmt.msc), so show current partitions (this is only for display purposes).
• Open CMD
• Type DISKPART (enter).
• Type LIST DISK (enter).
• Choose the disk that contains your WinRE partition. If it is disk zero, you type SELECT DISK 0.
• Type LIST PARTITION.
• Select the 100MB partition. If it were partition 1, you would type SELECT PARTITION 1.
• Type DETAIL PARTITION. Examine details to make sure this is the 100 WinRE partition.
• Type INACTIVE to make this no longer the active, bootable partition.
• Now select your Windows partition. If it is partition 2, you’ll type SELECT PARTITION 2.
• Again examine details with DETAIL PARTITION.
• Once you’re sure, mark it active with the command ACTIVE.
• Type EXIT to get out of Diskpart. You’re back at the commandline.
• You'll need to move the system files to the new bootloader drive. If that drive is C: use:
BCDBOOT c:\windows /s C:
• Taking a moment to show that the changes have shown up in Disk Management. The WinRE partition still shows as 'system' but not as 'active'.
• Now reboot the machine, and login again with admin privs.
• Open Disk Manager. The WinRE partition is no longer marked 'system' or 'active'.
• Delete the WinRE partition. You’re done.