You should be able to do it through the admin panel without his passsword? Just need to turn on the option to allow users to change their name, then change it, then turn the option back off?
unless roflforum doesn't allow you that access?
"There are 10 types of people in this world. Those who understand binary and those who don't."
"Humanity is quite amusing, when kept at a proper distance."- H. P. Lovecraft