Assuming you already have an ISO image or one Windows8 7 To create a bootable USB flash drive.

Step 1: Download Windows7 USB / DVD Download tool and install.

This tool is free from Microsoft, and so you can also get it from there. Despite its name, this tool works Windows8 ISO file as well. You can use this tool, any version of Windows.

Step 2: After you download and install the tool, run it, and now you need to browse, and to the path where the ISO file is located on your computer.

Step 3: Now select whether you want to create a bootable DVD window, or if you want it to be a U disk bootable. Here, you need to select the USB device, because you want to start the U disk.

Step 4: Browse and select your U want to make a bootable disk. U disk to ensure that there is atleast 4GB

Step 5: Once you start copying, use this tool to start creating Windows8 Windows8 ISO bootable USB flash drive is installed. Let this process is completed, and finally when you see the message "bootable USB device successfully created", you can restart the computer and boot from the USB drive.

So this is how I create a bootable USB Windows8 quick tutorial, I hope this will help you.