Login to the 1024 Domain Controller, then -

  1. Click the "Users and Computers" icon in the taskbar
  2. Find the user
  3. Right-click the user and select "Reset Password"

Generally you will reset to the standard password of "Red-green-blue1", unless the user has given you a specific password they want to use.  If resetting to the standard password, make sure to help the user change their password once they have logged in again.  (We can't use the option that forces them to change their password when they next login because we setting all user passwords to never expire)