about “How to boot a system with DVD or USB?”

After booting the system you will see the windows setup page. 

Now press Shift+F10  to open command prompt (CMD).

Step 2:  When the command prompt opened type fsutil fsinfo drives in order to list all available hard disk drives. See the screenshot.

You see all drives and D:\ must be the windows root directory because c:\ is the system reserved drive for windows boot loader.

To change the directory type d: and press enter then type cd windows\system32 and press enter.

Here you must change Utility manager (Utilman.exe) to cmd.exe. Before this take a backup of Utility manager file by typing ren Utilman.exe Utilman.bkp. 

Next copy cmd.exe and renamed to Utilman.exe by typing copy cmd.exe Utilman.exe. 

The Utility manager has been replaced with command prompt. Now you can restart you system withshutdown -r -t 0 command and boot it normally.

In the log in page of windows when you click on utility manager in the left corner of window the command prompt will open with full privilege.

With net user command you can create a new user, modify properties of existing user and reset it’s password.

Here I reset User name of Shais by typing net user shais 123.  

Now you can Login  with new password.

That’s all.