You have to elaborate more tech details here, if you wish to get help.
are you talking about the asus BackTracker, i.e asus's OS backup app ?
cause there are like 10K backup imaging apps in the market.

if i'm not mistaken, you can run BackTracker and create multiple DVD ( size like 15GB ) backup with it, but in the end it is just like an iso image file, so you can always copy them to where ever you want, bootable usb included.

Please connect this external disk to any computer, how does these files looks like ?
do you see: boot, EFI, en-us, Recovery, RecoveryImage, etc FOLDERS ?
if so, you can create a bootable USB ( note the total size of the total files ! ) just like you create windows bootable installation USB.
You can read in the following links how to create such a USB: ONE OPTION, another OPTION, another OPTION.
The only difference is that you pick your backtrack backup folder/iso/image file and NOT windows iso file when you create this booable usb.

Also, as I know asus made "wonderful job" as they release a "monster" laptop with it pre-installed windows on an mbr formatted disk runing on "legacy bios" -> you can create this bootable USB formatted as fat32 or NTFS (faster files copy to the usb with ntfs).
The important thing to note is when you LOAD the bootable USB, after it is ready for installation, using the boot-selection menu ( press ESC during POST, i.e just after laptop power on ) you MUST NOT select uefi:xxxxxxxxx ( x's is the usb name ) but either xxxxxxxxxx instead.

Also, you MUST set the CSM option in the bios to be enabled, beforehand, otherwise you'll just get UEFI:xxxxxx options in the boot-selection menu.

Now, for your own sake, please READ THE STICKY THREAD: Guide: How to install windows 8/8.1/10 The proper way (UEFI based installation)
so you'll be able to understand that using the pre-installed windows you got from asus is NOT A GOOD THING TO HAVE ON A FERRARI OF A LAPTOP !!!