NG15 how to create a boot disk

I recently bought NG15.  My son's computer's hard drive became stuck in a boot loop.  I ended up wiping the drive.  I have another computer that is an exactly the same with the same OS system.  I used NG15 to copy his drive.  I was able to sucessfully copy the drive and I can see the data, but when I try to boot using the usb it fails to boot and the drive disappears.  I should be able to boot using the USB.  I change the BIOs to boot to the USB first.  It fails.  What can I do to boot to this drive.  Should I reinstall the drive and then try booting...the issue is the drive is from an acer one computer..which requires the computer be totally reassembled...help!  How do I make a boot disk??