How to Make a USB Drive Bootable on Windows 7by Jim CampbellUpdated September 28, 2017
The Windows 7 operating system lets you boot from a USB flash drive in case your hard drive files are corrupted or they are accidentally deleted. You must format and partition the USB drive before you can use it to boot to Windows. Boot capabilities for a USB flash drive are accomplished using the Windows 7 Command Prompt utility and the Diskpart tool.
Insert the USB flash drive in the computer's USB port. Windows automatically detects the drive and creates a temporary drive letter for it. Click the Windows "Start" button in the taskbar and type "cmd" in the text box. Press "Ctrl," "Shift" and "Enter" to open the Command Prompt in Admin mode.
Type "diskpart" to start the disk partitioning tool. This tool adds boot files to the flash drive, and it partitions the drive for Windows 7. Type "list disk" to see a list of drives for the computer, including the flash USB drive.
Type "disk x," where "x" is the drive number listed for your USB drive in step 2, and press "Enter." This command activates the USB flash drive, so the rest of the commands you enter are executed on the flash drive.
Type the following commands line-by-line and press "Enter" to execute each one:
CLEAN CREATE PARTITION PRIMARY SELECT PARTITION 1 ACTIVE FORMAT FS=NTFS ASSIGN EXIT
BOOTSECT.EXE /NT60 x:
where "x" is your drive letter for the USB flash drive. This command copies the boot files from the Windows 7 computer to the flash drive.