Simple cmd.exe hacking for starters

These are a few hacking tricks that could come in handy sometime.
Go to 'Start' and click on 'Run'.The command Prompt shall pop up,it is a black fond with white letters.Then insert one of these codes:
This lets you see all the users connected on the computer
Code:
net user
This lets you change the password of any user (including the admin) unless you are using a network command line interface (eg. Powershell will only change the individual computers admin's password which is still pretty useful)
Code:
net user (username) *[note: just start typing the new password you want, no writting will come up though so just hit enter when you are done]
This adds a new user to the computer
Code:
net user (username) /add
This ones deletes a specific user
Code:
net user (username) /del
And last but not least this adds a new user to the local group
Code:
net localgroup (localgroup eg.administrators) (username) /add