Group wide password update

A friend of mine (the same friend of the 2 students who help with the network and the initial password leak) gives me the Admin password when I complain to him about the resolution of the PCs in my design class (1024x768 on 19" monitors). I get caught on the Admin user, they blame me for everybody knowing the password. They then pay the same 2 students, who get paid by the hour, to change the password on every PC by hand. Takes "10 minutes each". Takes hours to do. The school system also blames me for how much they had to pay. Monday I have to go back in front of the School Board and explain why they should "let" me back in. I don't want back in, but I do want to leave them speechless.

Long explanation, right? Here is the problem: Is there an easier way than that to change the windows password for every computer in a workgroup?