How to create a bootable USB Pendrive

How to create a bootable USB Pendrive............
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Tools Required:

1. USB flash drive with a minimum capacity of 4 GB.
2. Windows 7 Setup DVD.


Step 1 : Plug-in your USB flash drive.

Step 2 : Open the PowerShell (OR Command Prompt if PowerShell Not Exist). If you are using Windows 7/Vista then open it with administrator rights*.
"Goto Start -> All Programs -> Accessories ->Windows PowerShell ->  Right-click on “Windows PowerShell” and select “Run as Administrator”.

Step 3: In the PowerShell, type

DISKPART

This will start the Microsoft DiskPart utility as shown below:

Now issue the following command:
LIST DISK

This will show you a list of  available disks on your system. Disk 0 is usually the hard disk. In my case, Disk 1 is the USB drive (this can be a different one in your case). 
Now issue the command as shown below:

 SELECT DISK 1

above command, 1 is the USB drive number on my system. If you have a different number on your system, then you need to replace 1 with that number.
Step-4: Now issue the following list of commands one by one as shown below:

CLEAN
CREATE PARTITION PRIMARY
SELECT PARTITION 1
ACTIVE
FORMAT FS=NTFS QUICK
ASSIGN
EXIT

Close Power Shell and proceed to the next step.
Step 5: Insert the Windows 7/Vista installation disc and note down the “drive letter” of your DVD drive. In my case, it is “H:”.

Open the Command prompt. If you are using Windows 7/Vista then open it with administrator rights*.
* Goto Start -> All Programs -> Accessories -> Right-click on “Command Prompt” and select “Run as Administrator”.

Now type the following list of commands as shown below:
H:
CD BOOT
BOOTSECT.EXE /NT60 G:(NOTE:
G: is your USB drive letter)

EXIT

Step-6: Copy the contents of your Windows 7/Vista installation disk into the USB flash drive.
Directly Copy-Paste All DVD file into Usb Stick Then…

Your USB stick is now ready to boot and install the OS for you. Don’t forget to enable the “USB Boot” option and change the “Boot priority to USB device from hard disk” in your BIOS settings.

Tip: Remember that you'll need to make boot order change in the BIOS. See How To Change the Boot Order in BIOS if you need help doing that. 

Reference by:-http://www.geekomad.com/2011/10/create-bootable-usb-pen-drive-for.html#.US3JM6Wl6Fm