Firstly you must have domain admin rights on the account that you can log on with. If you do not have domain admin rights then the following will not work........
If you do then this will work:
Download the server admin pack from Microsoft, Install it on your desktop PC and then, once its installed, goto Start/Programs/Administrative Tools/User and Computers
From here, you should be able to see the AD for the domain, find your user (by using the search). Open the users properties, choose the Account tab and untick the box that says "Account is locked out"..........
Then all that remains is to re-educate the user who locked the account in the first place !!!