If you need to boot Windows from USB drive, remember that you need to have a bootable usb drive for Windows. Basically it is not enoght copy and paste the file you need for booting.
To do it we need to use the command DISKPART
How to use diskpart
From Start run cmd to have access to the command prompt.
The usb drive have to be connected to our PC. Run the command DISKPART and using the followings you will clear and format your usb-drive that will be now able to work at boot.
Be carefull because all your data on usb drive will be deleted and if you select the wrong drive you can do a big mistake.
SELECT DISK (usb)
CREATE PARTITION PRIMARY
SELECT PARTITION 1
Now you can copy and paste the data you need on the usb drive
Here is the screenshot with the commands: