How to make pendrive as bootable without any third party software in Windows
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1.Go to RUN(press Windows key+R)

2.Type "cmd" > enter and open with Administrator

3.Type "diskpart" > enter---diskpart is used to manag the disk operations in windows like
  create,delete partition,etc

4.Type "list disk" > enter---is used to show the disks are connected in your pc.

  In the list it show like

Disk 0  online 465 GB

Disk 1  online  8  GB

5.Type "select disk x" > enter --x means the disk number,select the pendrive disk number.

eg: select disk 1

6.Type "clean" > enter is used to clean all the files and partitions of the pendrive.

8.Type "create partition primary" > enter is used to create a primary partition.

9.Type "Select partition 1" > used to select the primary partition

10.Type "active"

11.Type "format fs=ntfs quick" used to format the partition with ntfs filesystem quickly.Dont forgot to mention
   quick other wise it will take more time.

12.exit from diskpar and copy the content of "WINDOWS 7 DVD" to the pendrive.

13.Restart the pc and Boot with pendrive