If you laptop came with 8.0 serial in bios and you are installing 8.1 setup will fail to read/apply it. Also if you get that same serial from your bios and add it to a autounattend.xml it will fail, what you need to do is use ei.cfg to skip the serial prompt and find another way to apply the 8.0 serial to your 8.1 image (I use dism to inject mine)