The USB device to repair windows is something that you would have had to have made when you first setup windows - Windows 8 Recovery Drive. If you didn't make one then you have two more options.
1. Try turning on or restarting the system while holding your shift key to access Advanced Startup Options and repair windows from there.
2. Use your Windows Installation disk to repair the Operating System by booting that before your OS.
If you don't have a disk, you can request one from Windows using your windows account (made when you first setup your computer) and product key from the system that has windows 8.
If you didn't make an account (like me) you can use this link to get the disk using another computer.
If you don't have a CD drive in that laptop, the link will also allow you to make a bootable Windows 8 USB flash drive.