this method only use in windows 7.
follow these steps one by one.
Insert usb drive in you computer. Start cmd.. the command prompt will appear. type these command in cmd.
diskpart → list disk → select disk → clean (this will erase the usb) → create partition primary → select partition 1 → active → format fs=ntfs (it will take 10-15 minutes)
After completed the format type again in command prompt assign (now you see your usb drive letter change) → exit (now you are exit fom disk part)
Now type the path to the executable file in your windows saved folder, ,ale sure that in your windows folder you have the boot folder with the bootsect executed file.
example the command goes like this E: → cd win7 sp1
→cdboot → bootsect/nt60h: (h is the letter of the usb drive) → exit.
now copy all the files in the windows folder to you usb drive.
Now you can see, your bootable usb is ready.

