How to create USB bootable windows 8:

   1.First download the windows 8 from this Link
 
   2.Download Windows 7 USB/DVD Download Tool from this Link and install it

   3.Launch the Windows 7 USB/DVD Download Tool
 
   4.Browse the file

   5. Click Begin copying

   6.Wait for the coplete process

Note : your pendrive must  formatted before you using that