how to make bootable usb windows 7

Step 1: Plug-in your USB flash drive(pen drive) to system. Your pen drive must be atleast 4 GB, 8 GB pendrive is best for this purpose

Step 2: Then run diskpart utility from command prompt, by typing ‘diskpart’ on command prompt and pressing enter. This will run the diskpart utility in a separate windows.

start --> cmd
c:\> diskpart

Step 3: diskpart console and type ‘list disk’ and press enter. This will list the various storage devices available. You can see the size column of the disk and here we can see that ‘disk 1′ is our pen drive. 

DISKPART> list disk

Step 4:  Then you have to run a series of commands. The commands to be run in the order are
 DISKPART>clean

DISKPART> select partition 1

DISKPART> create partition primary

DISKPART>format fs=fat32 quick

DISKPART>active
 Step 5: After the format is complete, put in your original Windows 7 DVD in your DVD drive, or if you have an .iso image of the DVD, mount that image using any virtual drive software like Power ISO.
or Extract the iso with winrar.