NOTE :- To creat this disk, it is neccessary to have minimum 4 gb pen drive

If you want to create bootable USB to install Windows xp, 7 or Vista then please follow the procedure below

Install Windows xp/7/Vista using bootable USB

Coming back to bootable USB guide, here we assume that you are using either Vista or Windows 7 to create a bootable USB.

1. Insert your USB to make it as bootable.

2. RIGHT CLICK ON Command Prompt WHICH IS IN THE START MENU , PROGRAM FILES , ACCESSORIES AND RUN IT AS ADMINISTRATOR OPTION, OR SHORTCUT KEY IS hit Ctrl + Shift + Enter.

3. When the Command Prompt opens, enter the following command:

DISKPART and hit enter.
LIST DISK and hit enter.
Once you enter the LIST DISK command, it will show the disk number of your USB drive. In the below image my USB drive disk no is Disk 1.

4. In this step you need to enter all the below commands one by one and hit enter. As these commands are self explanatory, you can easily guess what these commands do.
SELECT DISK 1 (Replace DISK 1 with your disk number)
CLEAN
CREATE PARTITION PRIMARY
SELECT PARTITION 1
ACTIVE
FORMAT FS=NTFS
(Format process may take few seconds)
ASSIGN
EXIT


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Do not close the command prompt as we need to execute one more command at the next step.

5. Insert your Windows DVD in the optical drive and note down the drive letter of the optical drive and USB media. Here I use “D” as my optical (DVD) drive letter and “H” as my USB drive letter.

6. Go back to command prompt and execute the following commands:

D:CD BOOT and hit enter. Where “D” is your DVD drive letter.
CD BOOT and hit enter to see the below message.
BOOTSECT.EXE/NT60 H:
(Where “H” is your USB drive letter)


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7. Copy Windows DVD contents to USB.
You are done with your bootable USB. You can now use this bootable USB as bootable DVD on any computer that comes with USB boot feature (most of the current motherboards support this feature).

after this just enjoy always with to load windows any time with your personal usb pen drive.