Process :

Step 1 :

Plug-in your pen drive in Laptop.

Step 2 :

Go to Start  >> Type Cmd  (in search program and file)  [Press Enter]
After pressing Enter command prompt will open.

On your Caps lock

Step 3 :

Type  DISKPART   [Press Enter]

Step 4 :

Type  LIST  DISK    [Press Enter]
It will show all available disk in your system. Disk 0 is usually hard disk of your system. In my case Disk 1 is Usb pen drive (This can be different in your case so plz make sure )

Step 5 :

Type  SELECT  DISK  1  [Press Enter]

Step 6 :

Type  CLEAN  [Press Enter]

Step 7 :

Type  CREATE  PARTITION  PRIMARY   [Press Enter]

Step 8 :

Type  SELECT  PARTITION  1  [Press Enter]

Step 9 :

Type  ACTIVE  [Press Enter]

Step 10 :

Type FORMAT  FS=NTFS  [Press Enter]
Wait Until 100% complete.

Step 11 :

Type  ASSIGN  [Press Enter]

Step 12 :

Type EXIT [Press Enter]

Now bootable usb pen drive is ready to use. After making this copy and paste windows 7 or 8 in your pen drive. It is easiest way to install windows 7 or 8 in your  system.

When you want to install windows, plug-in bootable pen drive and restart the system and press boot function key as per different system (f1——-f12) . but on the time of making only use pendrive not any other device or work.#anish