If you want to make a USB boot disk for Windows 7, make certain that you backup or remove all of the files that you have saved on the USB flash drive that you'll be using. You will need to reformat the drive and all of the files on it will be erased. Also check the BIOS (Basic Input Output System) to find out whether your computer is capable of booting from a USB flash drive.
Find a blank space on your desktop. Right-click on it and select "New" and then choose "Folder" from the drop-down menu. Create a name for the folder. Copy all of the contents on the USB flash drive into the new folder and save the files on your computer's hard drive, or another external drive. The USB flash drive must have 4 GB of available space on it.
Click the "Start" button on the taskbar and select the option "All Programs" from the menu list. Select "Accessories" and scroll down the list until you see "Command Prompt" and right-click on it. Click on "Run as Administrator" from the drop-down menu.
Type the command "DISKPART," without the quotes, and press the "Enter" key on your keyboard. You will see the message "Bootable USB Drive." Next, type the command "LIST DISK" and write down the Disk number for the USB flash drive.
Type the following commands and press the "Enter" key after typing each command. If the Disk number for your USB flash drive is Disk one use that number.
SELECT DISK 1
CREATE PARTITION PRIMARY
SELECT PARTITION 1
Minimise the Command Prompt window. Click the "-" symbol located near the top of the window. Insert your Windows 7 installation DVD disk into your CD/DVD drive. Check the drive letters of your DVD drive and the USB flash drive. Double-click "My Computer" on your desktop and write down the drive letters.
Maximise the Command Prompt window and type the command, "D: CD BOOT" and press the "Enter" key. (the letter "D" should be your CD/DVD drive letter).
Type the command "BOOTSECT.EXE /NT60 H:" to update the USB drive flash with BOOTMGR compatible code. (the letter "H" should be your USB flash drive) Copy all of the files on the Windows 7 installation disk to the USB flash drive. Close the Command Prompt window. Remove the disk from your CD/DVD drive and restart your computer.
Press the "F10," "Delete" or "ESC" key to enter your BIOS. Follow BIOS onscreen instructions and use the appropriate keys for navigating through the BIOS. Change the first boot sequence, so that your computer boots from the USB flash drive. Press the "ESC" key to save your settings and exist BIOS.