Are you asking about resetting your MtGox password? I think you are required to reset the password after you login through the claims site. However, if you can't login because you have forgotten your password, there is no option for resetting the password in this case. Your only option is to file a paper claim with the trustee. To do this, follow the "click here" link at the bottom of the login page on the claims site: https://claims.mtgox.com