A issue of restoring Windows7 system image

I experienced the trouble when restoring Windows7 system image from external USB HDD.  At first, I hypothesized that USB3.0 drivers didn't work well.  However, from my some investgations, Windows7 system image recovery program might lose recovery images if multiple images (or different versions) were stored in "WindowsImageBackup"  folder of the same HDD.  I had stored Windows8.1 (x64, UEFI) image in that folder as well as Windows7 system image (x64, MBR).  After I moved my Windows8.1 system image to another folder, Windows7 recovery program could recgnize my system image properly.