How to Change a Password in Windows XP Using CMD

Changing a password (XP, sometimes works on Vista):

Go to Start, Run, cmd
Type "net user" (Without Quotes)

It will show a list of your user account names. If you have ever re-named an account, it will show the origonal name. It may also have account(s) which you do not know about.

Pick an account and type "net user (Account name) *" (Without Quotes or brackets)
Type in the new password and press enter. Repeat.

Do not worry if it does not show your password, it is not meant to, so if it looks like you havent typed a password, you are doing it right.
All done!

Backdoor XP login: (Without a password)

Re-boot the computer and when it comes up with the welcome screen with all the account names and pictures, simultaneously press "CTRL, ALT and DELETE".
A new screen should pop up, if it dosent, then press the combination again.
When the screen pops up, in the username text box, type "Administrator". Leave the password blank and press "Login" or "OK".
If it says that the password is incorrect, you or whoever set it up was trying to make your computer secure by locking the Admin account with a password. I suggest you go and visit a computer shop and get them to hack it for you.