A simple way to make USB Bootable. 1. You need a USB drive (Make sure it not fake) with size of 4GB or More. 2. Back up all data stored in the USB Drive. 3. Format a USB Drive using NTFS file system, see the figure below. 4. After completing the formatting process, copy the contents of windows 7 or windows 8 into the USB Drive, but if you have an image file like .ISO or else extract the file to get its contents and copy them to a USB Drive. 5. Close all windows and restart your computer. 6. Make sure booting sequence is from USB Drive by changing boot options in BIOS settings (Press the prompted key to enter BIOS settings depending on the type of your Computer). 7. Follow the windows installing instructions and you are done!!.