Kal took Leo's advice and created a second user account for his wife, so she wouldn't be using the administrator account for day to day use. But then he lost the administrator password. Leo says there are bootable discs that he can use to reset the password. Here's a support document from Microsoft that will help him reset the password. He can use another computer to create this disc.
Another option is a program called Ophcrack, but that will only work if the password isn't as long and secure. NT Offline Password Reset could also work.
The chatroom recommends going to pogostick.net/~pnh/ntpasswd/, which Leo says is probably the one he'll want.