What you needed ?
- an ISO image of windows 8 (Windows 7 also works with this method)or DVD media
 
- 8Gb Pendrive (depends on iso size if less than 4 gb you need 4 gb Pendrive )  
 
- Windows 7 or Windows 8 installed PC 
 
- Daemon tool or Winrar to mount iso image (here i an using Daemon tool)
 
-   
+

 
 
First click on start button and type cmd then select cmd from search result and right click then open it as administrator
it will ask you for permission click yes 
then you can see command prompt 
connect your pendrive to your pc 
now type in the command prompt 
now it will load a system program called disk part 
then type 
now it will show you all partitions in pc including pendrive 
then select pendrive with its number by typing 
 select disk  ( your pendrive number here )
 
now type 
then select your pendrive volume with your volume number like this 
  select  volume (your volume number here)
 
now type 
then type 
  format fs=ntfs label="Windows 8 USB"
OR
type 
 format fs=ntfs label="Windows 8 USB" quick 
for quick format 
some times quick format does not works thats why i have used normal format 
 
*Note 
here format =  is command for format
fs= which  file format to select like ntfs , fat etc 
label = drive name 
this will take few more times to complete 
its completed 
now type 
*NOTE 
assign is a command used for give Drive letter to a partition with out giving assign ! you cant mount partition 
now type
then open Windows 8 USB drive 
then mount your iso image using (daemon tool or Winrar )or insert your Windows 8 DVD to pc 
then copy all files in your Media to your USB Drive 
eject USB drive after copying then reboot , change first boot order from bios to USB drive 
enjoy