How To format computer with the use of usb only Step by step

1. plug ur 4 gb usb pen drive
2. go to cmd promt run as administrator
3. type the following-
diskpart
list disk
the number of ur usb vl be listed. ( assume usb drive is disk 1 ) ,then type-
select disk 1
clean
create partition primary
select partition 1
active
format fs=NTFS
assign
exit
( now ur usb is bootable )
4. copy the windows vista\windows 7 dvd to ur usb
5. restart ur computer
6. go to bios
7.then go to boot option
8. select boot from usb and press enter
9. Thanks all enjoy