We have Windows OS .iso files but we do not have optical drive, also we need to install Windows OS to some new computers which had not installed any OS yet, so let us build bootable USB drive from .iso file.
1: Get the tool and install it:
Windows 7 USB/DVD download tool
2: Now you can use the tool, very simple, just specify the .iso file and following steps:
3: Note when you see the following screen please select USB device
4: Select right USB and Click begin copying button to start a bootable USB making process:
You will see the message that all files on the USB will have to be deleted, otherwise you can not get a bootable USB.
The copy process will take some time:
After it done, you will get a bootable USB with Windows OS system, you can use it to boot your computer, and install Windows OS now.