Creating bootable USB for win7

option 1:

Task 1: Making the USB drive an Active Primary Partition.

1. Open a command prompt (with administrative rights if required by your OS).
2. At the command Prompt type Diskpart and press enter
3. Type List Disk and press enter
4. You will see a list of all the disks on your computer.. A number will identify each disk.
   1. If you do not know which disk is you USB drive go through the list by typing Select Disk 1 enter and then type details. repeat until you know you are on the right USB drive. Hint: It is probably the last one.
5. Type select disk 4* and press enter. The system will report: "Disk 4* is now selected" (*Where disk 4 is the number of the USB drive, change this number to reflect your system).
6. Type Clean and press enter. The system will report "DiskPart succeeded in cleaning the disk." This will remove the disk from your current drive letter for your USB.
7. Type create partition primary and press enter. The system will report "DiskPart succeeded in creating the specified partition."
8. Type select partition 1 and press enter. The system will report "Partition 1 is now the selected partition."
9. Type active and press enter. The system will report "DiskPart Marked the current partition as active."
10. Type assign and press enter.  The system will report "DiskPart successfully assigned a drive letter ..."
11. Type detail disk and press enter. Details will be listed and under the column heading "LTR" you will see the drive letter. I will assume it is U: for the remainder of the explanation.
12. Type  exit  and press enter. This will leave the DiskPart context.
    

Task 2: Formating the USB Drive and copying the install files.

for cd mapping use magioiso -- magicdisk.

1. If the command prompt is not still open, open the command prompt.
2. Type format U: /fs:fat32 /q and press enter. (Where U: is the letter of your USB Drive)
3. A warning will appear indicating all information on the drive will be lost. Type Y and press enter.
4. You will be prompted to enter a label for the drive. Press enter to continue.
5. We have now formatted the drive and can proceed to copying the files. Assuming Drive d: for DVD and Drive u: for USB
6. Type xcopy d:\*.* /s/e/f u:\  . The files will copy and may take a long time depending on the USB drive performance.

 option 2:

use windows 7 usb dvd download tool

create  a bootable usb with the same bit version and os system..
otherwise it won't work...